Pnge 200 Homework 10 Grade

This chapter explains the basic syntaxes of the Java programming language. I shall assume that you could write some simple Java programs. (Otherwise, read "Introduction To Java Programming for First-time Programmers".)

To be a proficient programmer, you need to master two things: (1) the syntax of the programming language, and (2) the libraries associated with the language.

You may also try the "Exercises on Java Basics".

Basic Syntaxes


The steps in writing a Java program is illustrated as follows:

Step 1: Write the source codes () using a programming text editor (such as Notepad++, Textpad, gEdit) or an (such as Eclipse or NetBeans).

Step 2: Compile the source codes () into Java portable bytecode () using the JDK compiler ("").

Step 3: Run the compiled bytecode () with the input to produce the desired output, using the Java Runtime ("").

Below is a simple Java program that demonstrates the three basic programming constructs: sequential, loop, and conditional. Read "Introduction To Java Programming for First-time Programmers" if you need help in understanding this program.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 public class OddEvenSum { public static void main(String[] args) { int lowerbound = 1, upperbound = 1000; int sumOdd = 0; int sumEven = 0; int number = lowerbound; while (number <= upperbound) { if (number % 2 == 0) { sumEven += number; } else { sumOdd += number; } ++number; } System.out.println("The sum of odd numbers from " + lowerbound + " to " + upperbound + " is " + sumOdd); System.out.println("The sum of even numbers from " + lowerbound + " to " + upperbound + " is " + sumEven); System.out.println("The difference between the two sums is " + (sumOdd - sumEven)); } }

The expected outputs are:

The sum of odd numbers from 1 to 1000 is 250000 The sum of even numbers from 1 to 1000 is 250500 The difference between the two sums is -500


Comments are used to document and explain your codes and your program logic. Comments are not programming statements. They are ignored by the compiler and have no consequences to the program execution. Nevertheless, comments are VERY IMPORTANT for providing documentation and explanation for others to understand your programs (and also for yourself three days later).

There are two kinds of comments in Java:

  1. Multi-Line Comment: begins with a and ends with a , and can span multiple lines.
  2. End-of-Line (Single-Line) Comment: begins with and lasts till the end of the current line.

I recommend that you use comments liberally to explain and document your codes. During program development, instead of deleting a chunk of statements irrevocably, you could comment-out these statements so that you could get them back later, if needed.

Statements and Blocks

Statement: A programming statement is the smallest independent unit in a program, just like a sentence in the English language. It performs a piece of programming action. A programming statement must be terminated by a semi-colon (), just like an English sentence ends with a period. (Why not ends with a period like an English sentence? This is because period crashes with decimal point - it is hard for the dumb computer to differentiate between period and decimal point in the early days of computing!)

For examples,

int number1 = 10; int number2, number3=99; int product; product = number1 * number2 * number3; System.out.println("Hello");

Block: A block is a group of statements surrounded by a pair of curly braces . All the statements inside the block is treated as one single unit. Blocks are used as the body in constructs like class, method, if-else and for-loop, which may contain multiple statements but are treated as one unit (one body). There is no need to put a semi-colon after the closing brace to end a compound statement. Empty block (i.e., no statement inside the braces) is permitted. For examples,

if (mark >= 50) { System.out.println("PASS"); System.out.println("Well Done!"); System.out.println("Keep it Up!"); } if (number == 88) { System.out.println("Got it!"); } else { System.out.println("Try Again!"); } i = 1; while (i < 8) { System.out.print(i + " "); ++i; } public static void main(String[] args) { ...statements... }

White Spaces and Formatting Source Codes

White Spaces: Blank, tab and newline are collectively called white spaces. Java, like most of the computing languages, ignores extra white spaces. That is, multiple contiguous white spaces are treated as a single white space.

You need to use a white space to separate two keywords or tokens to avoid ambiguity, e.g.,

int sum=0; double average;

Additional white spaces and extra lines are, however, ignored, e.g.,

int sum = 0 ; double average ;

Formatting Source Codes: As mentioned, extra white spaces are ignored and have no computational significance. However, proper indentation (with tabs and blanks) and extra empty lines greatly improves the readability of the program. This is extremely important for others (and yourself three days later) to understand your programs.

For example, the following one-line hello-world program works. But can you read and understand the program?

public class Hello{public static void main(String[] args){System.out.println("Hello, world!");}}

Braces: Java's convention is to place the beginning brace at the end of the line, and align the ending brace with the start of the statement.

Indentation: Indent each level of the body of a block by an extra 3 (or 4) spaces.

public class ClassName { public static void main(String[] args) { statement; statement; if (test) { statements; } else { statements; } init; while (test) { statements; update; } } }

Variables and Types


Computer programs manipulate (or process) data. A variable is used to store a piece of data for processing. It is called variable because you can change the value stored.

More precisely, a variable is a named storage location, that stores a value of a particular data type. In other words, a variable has a name, a type and stores a value.

  • A variable has a name (aka identifier), e.g., , , , and . The name is needed to uniquely identify each variable, so as to assign a value to the variable (e.g., ), as well as to retrieve the value stored (e.g., ).
  • A variable has a type. Examples of Java type are:
    • : meant for integers (whole numbers) such as and .
    • : meant for floating-point (real numbers), such as , , , , having a optional decimal point and fractional part.
    • : meant for texts such as , . Strings are enclosed within a pair of double quotes.
    • : meant for a single character, such as , . A char is enclosed by a pair of single quotes.
  • A variable can store a value of that particular data type. It is important to take note that a variable in most programming languages is associated with a type, and can only store value of the particular type. For example, a variable can store an integer value such as , but NOT real number such as , nor string such as .
  • The concept of type was introduced in the early programming languages to simplify interpretation of data made up of binary numbers ('s and 's). The type determines the size and layout of the data, the range of its values, and the set of operations that can be applied.

The following diagram illustrates three types of variables: , and . An variable stores an integer (or whole number or fixed-point number); a variable stores a floating-point number or real number; a variable stores texts.

Identifiers (or Names)

An identifier is needed to name a variable (or any other entity such as a method or a class). Java imposes the following rules on identifiers:

  • An identifier is a sequence of characters, of any length, comprising uppercase and lowercase letters , digits , underscore , and dollar sign .
  • White space (blank, tab, newline) and other special characters (such as , , , , , , commas, etc.) are not allowed. Take note that blank and dash () are not allowed, i.e., "" and "" are not valid names. (This is because blank creates two tokens and dash crashes with minus sign!)
  • An identifier must begin with a letter or underscore (). It cannot begin with a digit (because that could confuse with a number). Identifiers begin with dollar sign () are reserved for system-generated entities.
  • An identifier cannot be a reserved keyword or a reserved literal (e.g., , , , , , , , , ).
  • Identifiers are case-sensitive. A is NOT a , and is NOT a .

Caution: Programmers don't use blank character in names. It is either not supported (e.g., in Java and C/C++), or will pose you many more challenges.

Variable Naming Convention

A variable name is a noun, or a noun phrase made up of several words with no spaces between words. The first word is in lowercase, while the remaining words are initial-capitalized. For example, , , , , and . This convention is also known as camel-case.

  1. It is important to choose a name that is self-descriptive and closely reflects the meaning of the variable, e.g., or , but not or , to store the number of students. It is okay to use long names!
  2. Do not use meaningless names like , , , , , , , , .
  3. Avoid single-letter names like , , , , , , which is easier to type but often meaningless. Exception are common names like , , for coordinates, for index. Long names are harder to type, but self-document your program. (I suggest you spend sometimes practicing your typing.)
  4. Use singular and plural nouns prudently to differentiate between singular and plural variables.  For example, you may use the variable to refer to a single row number and the variable to refer to many rows (such as an array of rows - to be discussed later).

Variable Declaration

To use a variable in your program, you need to first "introduce" it by declaring its name and type, in one of the following syntaxes. The act of declaring a variable allocates a storage (of size capable of holding a value of the type).

type identifier;type identifier1,identifier2, ...,identifierN;type identifier=initialValue;type identifier1=initValue1, ...,identifierN=initValueN;  int option;   double sum, difference, product, quotient;   int magicNumber = 88;   String greetingMsg = "Hi!", quitMsg = "Bye!";

Take note that:

  • Java is a "strongly type" language. A variable is declared with a type. Once the type of a variable is declared, it can only store a value belonging to this particular type. For example, an variable can hold only integer such as , and NOT floating-point number such as or text string such as .
  • Each variable can only be declared once.
  • You can declare a variable anywhere inside the program, as long as it is declared before used.
  • The type of a variable cannot be changed inside the program, after it is declared.
  • A variable declaration statement begins with a type, and works for only that type. In other words, you cannot declare variables of two different type in a single declaration statement.

Constants (final Variables)

Constants are non-modifiable variables, declared with keyword . Their values cannot be changed during program execution. Also, constants must be initialized during declaration. For examples:

final double PI = 3.1415926;

Constant Naming Convention: Use uppercase words, joined with underscore. For example, , .


An expression is a combination of operators (such as addition , subtraction , multiplication , division ) and operands (variables or literals), that can be evaluated to yield a single value of a certain type. For example,

1 + 2 * 3 int sum, number; sum + number double principal, interestRate; principal * (1 + interestRate)


An assignment statement:

  1. assigns a literal value (of the ) to a variable (of the ), e.g., ; or
  2. evaluates an expression (of the RHS) and assign the resultant value to a variable (of the LHS), e.g., .

The syntax for assignment statement is:

variable=literalValue;variable=expression;  number = 88;   sum = sum + number;

The assignment statement should be interpreted this way: The expression on the right-hand-side (RHS) is first evaluated to produce a resultant value (called r-value or right-value). The r-value is then assigned to the variable on the left-hand-side (LHS) or l-value. Take note that you have to first evaluate the RHS, before assigning the resultant value to the LHS. For examples,

number = 8; number = number + 1; 8 = number; // INVALID number + 1 = sum; // INVALID

In Java, the equal symbol is known as the assignment operator. The meaning of in programming is different from Mathematics. It denotes assignment of the LHS value to the RHS variable, instead of equality of the RHS and LHS. The RHS shall be a literal value or an expression that evaluates to a value; while the LHS must be a variable.

Note that is valid (and often used) in programming. It evaluates and assign the resultant value to the variable . illegal in Mathematics.

While is allowed in Mathematics, it is invalid in programming (because the LHS of an assignment statement must be a variable).

Some programming languages use symbol "", "" or "" as the assignment operator to avoid confusion with equality.

Primitive Types

In Java, there are two broad categories of types: primitive types (e.g., , ) and reference types (e.g., objects and arrays). We shall describe the primitive types here and the reference types (classes and objects) in the later chapters on "Object-Oriented Programming".

byteInteger8-bit signed integer
The range is
short16-bit signed integer
The range is
int32-bit signed integer
The range is (≈9 digits)
long64-bit signed integer
The range is (≈19 digits)
32-bit single precision floating-point number
(6-7 significant decimal digits, in the range of )
double64-bit double precision floating-point number
(14-15 significant decimal digits, in the range of )
Represented in 16-bit Unicode to .
Can be treated as 16-bit unsigned integers in the range of in arithmetic operations.
Takes a value of either or .
The size of is not defined in the Java specification, but requires at least one bit.
Built-in Primitive Types

Primitive type are built-in to the languages. Java has eight primitive types, as listed in the above table:

  • There are four integer types: 8-bit , 16-bit , 32-bit and 64-bit . They are signed integers in 2's complement representation, and can hold an integer value of the various ranges as shown in the table.
  • There are two floating-point types: 32-bit single-precision and 64-bit double-precision , represented as specified by IEEE 754 standard. A can represent a number between and , approximated. A can represented a number between and , approximated. Take note that not all real numbers can be represented by and . This is because there are infinite real numbers even in a small range of say , but there is a finite number of patterns in a n-bit representation. Most of the floating-point values are approximated to their nearest representation.
  • The type represents a single character, such as , , . In Java, char is represented using 16-bit Unicode (in UCS-2 format) to support internationalization (i18n). A can be treated as a 16-bit unsigned integer (in the range of ) in arithmetic operations. For example, character is (decimal) or (hexadecimal); character is (decimal) or (hexadecimal); character is (decimal) or (hexadecimal).
  • Java introduces a new binary type called "", which takes a value of either or .

Example: The following program can be used to print the maximum, minimum and bit-length of the primitive types. The maximum, minimum and bit-size of are kept in constants , , .

public class PrimitiveTypesMinMax { public static void main(String[] args) { System.out.println("int(min) = " + Integer.MIN_VALUE); System.out.println("int(max) = " + Integer.MAX_VALUE); System.out.println("int(bit-length) = " + Integer.SIZE); System.out.println("byte(min) = " + Byte.MIN_VALUE); System.out.println("byte(max) = " + Byte.MAX_VALUE); System.out.println("byte(bit-length)=" + Byte.SIZE); System.out.println("short(min) = " + Short.MIN_VALUE); System.out.println("short(max) = " + Short.MAX_VALUE); System.out.println("short(bit-length) = " + Short.SIZE); System.out.println("long(min) = " + Long.MIN_VALUE); System.out.println("long(max) = " + Long.MAX_VALUE); System.out.println("long(bit-length) = " + Long.SIZE); System.out.println("char(min) = " + (int)Character.MIN_VALUE); System.out.println("char(max) = " + (int)Character.MAX_VALUE); System.out.println("char(bit-length) = " + Character.SIZE); System.out.println("float(min) = " + Float.MIN_VALUE); System.out.println("float(max) = " + Float.MAX_VALUE); System.out.println("float(bit-length) = " + Float.SIZE); System.out.println("double(min) = " + Double.MIN_VALUE); System.out.println("double(max) = " + Double.MAX_VALUE); System.out.println("double(bit-length) = " + Double.SIZE); } }

The expected outputs are:

int(min) = -2147483648 int(max) = 2147483647 int(bit-length) = 32 byte(min) = -128 byte(max) = 127 byte(bit-length)=8 short(min) = -32768 short(max) = 32767 short(bit-length) = 16 long(min) = -9223372036854775808 long(max) = 9223372036854775807 long(bit-length) = 64 char(min) = 0 char(max) = 65535 char(bit-length) = 16 float(min) = 1.4E-45 float(max) = 3.4028235E38 float(bit-length) = 32 double(min) = 4.9E-324 double(max) = 1.7976931348623157E308 double(bit-length) = 64

Another commonly-used type is , which represents texts (a sequence of characters) such as . is not a primitive type, and will be further elaborated later. In Java, a is enclosed by single quotes (e.g., , ), while a is enclosed by double quotes (e.g., ). For example,

String message = "Hello, world!"; char gender = 'm';
Choice of Data Types for Variables

As a programmer, you need to choose variables and decide on the type of the variables to be used in your programs. Most of the times, the decision is intuitive. For example, use an integer type for counting and whole number; a floating-point type for number with fractional part, for text message, for a single character, and for binary outcomes.

Rules of Thumb
  • Use for integer and for floating point numbers. Use , , and only if you have a good reason to choose that specific precision.
  • Use for counting and indexing, NOT floating-point type ( or ). This is because integer type are precise and more efficient in operations.
  • Use an integer type if possible. Use a floating-point type only if the number contains a fractional part.
Data Representation

Read "Data Representation" if you wish to understand how the numbers and characters are represented inside the computer memory. In brief, It is important to take note that char is different from , , , , , and . They are represented differently in the computer memory, with different precision and interpretation. For example, is , is , is , is , is , is , is , and is a complex object.

There is a subtle difference between and .

Furthermore, you MUST know the type of a value before you can interpret a value. For example, this value cannot be interpreted unless you know its type (or its representation).

Example (Variable Names and Types): Paul has bought a new notebook of "abc" brand, with a processor speed of 3.2GHz, 4 GB of RAM, 500GB hard disk, with a 15-inch monitor, for $1650.45. He has chosen service plan 'B' among plans 'A', 'B' and 'C', plus on-site servicing. Identify the data types and name the variables.

The possible variable names and types are:

String name = "Paul"; String brand = "abc"; double processorSpeedInGHz = 3.2; double ramSizeInGB = 4; int harddiskSizeInGB = 500; int monitorInInch = 15; double price = 1650.45; char servicePlan = 'B'; boolean onSiteService = true;

Exercise (Variable Names and Types): You are asked to develop a software for a college. The system shall maintain information about students. This includes name, address, phone number, gender, date of birth, height, weight, degree pursued (e.g., B.Sc., B.A.), year of study, average GPA, with/without tuition grant, is/is not a scholar. Each student is assigned a unique 8-digit number as id. Identify the variables. Assign a suitable name to each variable and choose an appropriate type. Write the variable declaration statements.

Literals for Primitive Types and String

A literal, or literal constant, is a specific constant value, such as , , , , , , that is used in the program source. It can be assigned directly to a variable; or used as part of an expression. They are called literals because they literally and explicitly identify their values. We call it literal to distinguish it from a variable.

Integer (, , , ) literals

A whole number, such as and , is treated as an by default. In Java, the range of 32-bit literals is () to (). For example,

int number = -123; int sum = 1234567890; int bigSum = 8234567890;

An literal may precede with a plus () or minus () sign, followed by digits. No commas or special symbols (e.g., or space) is allowed (e.g., and are invalid). No preceding is allowed too (e.g., is invalid).

You can use a prefix (zero) to denote a value in octal, and prefix (or ) for a value in hexadecimal, e.g.,

int number = 1234; int number = 01234; int number = 0x1abc;

(JDK 1.7) From JDK 7, you can use prefix '' or '' to specify a value in binary. You are also permitted to use underscore () to break the digits into groups to improve the readability. But you must start and end the literal with a digit. For example,

int number1 = 0b01010000101000101101000010100010; int number2 = 0b0101_0000_1010_0010_1101_0000_1010_0010; int number3 = 2_123_456;

A literal above the range requires a suffix or (avoid lowercase, which confuses with the number one), e.g., , . In Java, the range of 64-bit literals is () to (). For example,

long bigNumber = 1234567890123L; long sum = 123;

No suffix is needed for and literals. But you can only use integer values in the permitted range. For example,

byte smallNumber = 12345; byte smallNumber = 123; short midSizeNumber = -12345;
Floating-point (, ) literals

A number with a decimal point, such as and , is treated as a by default. You can also express them in scientific notation, e.g., , , where or denotes the exponent in base of 10. You could precede the fractional part or exponent with a plus () or minus () sign. Exponent values are restricted to integer. There should be no space or other characters in the number.

You can optionally use suffix or to denote literals.

You MUST use a suffix of or for literals, e.g., . For example,

float average = 55.66; float average = 55.66f;
Character () Literals and Escape Sequences

A printable literal is written by enclosing the character with a pair of single quotes, e.g., , , and . In Java, characters are represented using 16-bit Unicode, and can be treated as a 16-bit unsigned integers in arithmetic operations. In other words, and 16-bit unsigned integer are interchangeable. You can also assign an integer in the range of to a variable.

For example,

char letter = 'a'; char anotherLetter = 98; System.out.println(letter); System.out.println(anotherLetter); anotherLetter += 2; System.out.println(anotherLetter);

Non-printable and control characters can be represented by a so-called escape sequence, which begins with a back-slash () followed by a pattern. The commonly-used escape sequences are:

Escape SequenceDescriptionUnicode in Hex (Decimal)
\nNewline (or Line-feed)000AH (10D)
\rCarriage-return000DH (13D)
\tTab0009H (9D)
\"Double-quote0022H (34D)
\'Single-quote0027H (39D)
\\Back-slash005CH (92D)
\uhhhhUnicode number hhhh (in hex),
e.g., \u000a is newline, \u60a8 is 您, \u597d is 好


  • Newline () and Carriage-Return (), represented by the escape sequence , and respectively, are used as line delimiter (or end-of-line, or EOL). Take note that Unixes and Mac use () as EOL, while Windows use ().
  • Horizontal Tab () is represented as .
  • To resolve ambiguity, characters back-slash (), single-quote () and double-quote () are represented using escape sequences , and , respectively. E.g.,
    • To represent a back-slash , you need to write , instead of , as a back-slash begins an escape sequence. Similarly, to include a back-slash in a double-quoted string, you need to write .
    • To represent a single-quote , you need to write to distinguish it from the closing single-quote. But you can write double-quote directly, i.e., .
    • To place a double-quote in a double-quoted string, you need to use to distinguish it from the closing double-quote, e.g., . But you can write single-quote directly, e,g, .
  • Other less commonly-used escape sequences are: for alert or bell, for backspace, for form-feed, for vertical tab. These may not be supported in some consoles.
String Literals

A literal is composed of zero of more characters surrounded by a pair of double quotes, e.g., , . For example,

String directionMsg = "Turn Right"; String greetingMsg = "Hello"; String statusMsg = "";

String literals may contains escape sequences. Inside a , you need to use for double-quote to distinguish it from the ending double-quote, e.g. . Single-quote inside a does not require escape sequence. For example,

System.out.println("Use \\\" to place\n a \" within\ta\tstring"); Use \" to place a " within a string

Exercise: Write a program to print the following animal picture using multiple . Take note that you need to use escape sequences to print special characters.

'__' (oo) +========\/ / || %%% || * ||-----|| "" ""
boolean Literals

There are only two literals, i.e., and . For example,

boolean done = true; boolean gameOver = false;
Example on Literals
public class LiteralTest { public static void main(String[] args) { String name = "Tan Ah Teck"; char gender = 'm'; boolean isMarried = true; byte numChildren = 8; short yearOfBirth = 1945; int salary = 88000; long netAsset = 8234567890L; double weight = 88.88; float gpa = 3.88f; System.out.println("Name is " + name); System.out.println("Gender is " + gender); System.out.println("Is married is " + isMarried); System.out.println("Number of children is " + numChildren); System.out.println("Year of birth is " + yearOfBirth); System.out.println("Salary is " + salary); System.out.println("Net Asset is " + netAsset); System.out.println("Weight is " + weight); System.out.println("GPA is " + gpa); } }

The expected outputs are:

Name is Tan Ah Teck
Gender is m
Is married is true
Number of children is 8
Year of birth is 1945
Salary is 88000
Net Asset is 8234567890
Weight is 88.88
GPA is 3.88


Arithmetic Operators

Java supports the following arithmetic operators:

*Multiplicationexpr1 * expr22 * 3 → 6
3.3 * 1.0 → 3.3
/Divisionexpr1 / expr21 / 2 → 0
1.0 / 2.0 → 0.5
%Remainder (Modulus)expr1 % expr25 % 2 → 1
-5 % 2 → -1
5.5 % 2.2 → 1.1
(or unary positive)
expr1 + expr2
1 + 2 → 3
1.1 + 2.2 → 3.3
(or unary negate)
expr1 - expr2
1 - 2 → -1
1.1 - 2.2 → -1.1

All these operators are binary operators, i.e., they take two operands. However, '+' and '-' can also be interpreted as unary "positive" and "negative" operators. For example,

int number = -88; int x = +5;

Arithmetic Expressions

In programming, the following arithmetic expression:

must be written as . You cannot omit the multiplication symbol (), as in Mathematics.

Rules on Precedence

Like Mathematics:

  1. The multiplication (), division () and remainder () take precedence over addition () and subtraction (). For example, is interpreted as .
  2. Unary (positive) and (negate) have higher precedence.
  3. Parentheses have the highest precedence and can be used to change the order of evaluation.
  4. Within the same precedence level (e.g., addition and subtraction), the expression is evaluated from left to right (called left-associative). For example, is evaluated as and is .

Mixed-Type Operations

The arithmetic operators are only applicable to primitive numeric types: , , , , , , and .These operators do not apply to .

If both operands are , , or , the arithmetic operations are carried in that type, and evaluated to a value of that type, i.e., ; .

It is important to take note division produces an , i.e., , with the result truncated, e.g., , instead of ?!

If both operand are , or , the operations are carried out in , and evaluated to a value of . A is treated as a 16-bit unsigned integer in the range of . For example, .

If the two operands belong to different types, the value of the smaller type is promoted automatically to the larger type (known as implicit type-casting). The operation is then carried out in the larger type, and evaluated to a value in the larger type.

  • , or is first promoted to before comparing with the type of the other operand.
  • The order of promotion is: .

For examples,

  1. . Hence, .
  2. .
  3. (You probably don't expect this answer!)
  4. (The result is an , NOT !) byte b1 = 1, b2 = 2; byte b3 = b1 + b2;

The type-promotion rules for binary operations can be summarized as follows:

  1. If one of the operand is , the other operand is promoted to ;
  2. Else If one of the operand is , the other operand is promoted to ;
  3. Else If one of the operand is , the other operand is promoted to ;
  4. Else both operands are promoted to .

The type-promotion rules for unary operations (e.g., negate ) can be summarized as follows:

  1. If the operand is , , or , there is no promotion.
  2. Else (the operand is , , ), the operand is promoted to .

For example,

byte b1 = 1; byte b2 = -b1;
Remainder (Modulus) Operator

To evaluate the remainder (for negative and floating-point operands), perform repeated subtraction until the absolute value of the remainder is less than the absolute value of the second operand.

For example,


    Java does not have an exponent operator. (The operator is for exclusive-or, NOT exponent). You need to use method to evaluate raises to power .


    Study the output of the following program:

    public class OverflowTest { public static void main(String[] args) { int i1 = 2147483647; System.out.println(i1 + 1); System.out.println(i1 + 2); System.out.println(i1 * i1); int i2 = -2147483648; System.out.println(i2 - 1); System.out.println(i2 - 2); System.out.println(i2 * i2); } }

    In arithmetic operations, the resultant value wraps around if it exceeds its range (i.e., overflow). Java runtime does NOT issue an error/warning message but produces an incorrect result.

    On the other hand, integer division produces an truncated integer and results in so-called underflow. For example, gives , instead of . Again, Java runtime does NOT issue an error/warning message, but produces an imprecise result.

    It is important to take note that checking of overflow/underflow is the programmer's responsibility. i.e., your job!!!

    Why computer does not flag overflow/underflow as an error? This is due to the legacy design when the processors were very slow. Checking for overflow/underflow consumes computation power. Today, processors are fast. It is better to ask the computer to check for overflow/underflow (if you design a new language), because few humans expect such results.

    To check for arithmetic overflow (known as secure coding) is tedious. Google for "INT32-C. Ensure that operations on signed integers do not result in overflow" @


    In Java, you will get a compilation error if you try to assign a or value of to an variable. This is because the fractional part would be lost. The compiler issues an error "possible loss in precision". For example,

    double d = 3.5; int i; i = d;int sum = 55.66f;
    Explicit Type-Casting and Type-Casting Operator

    To assign the a value to an variable, you need toinvoke the so-called type-casting operator - in the form of - to operate on the operand and return a truncated value in . In other words, you tell the compiler you concisely perform the truncation and you are aware of the possible loss of precision. You can then assign the truncated value to the variable. For example,

    double d = 3.5; int i; i = (int) d;

    Type-casting is an operation which takes one operand. It operates on its operand, and returns an equivalent value in the specified type.

    There are two kinds of type-casting in Java:

    1. Explicit type-casting via a type-casting operator in the prefix form of , as described above, and
    2. Implicit type-casting performed by the compiler automatically, if there is no loss of precision.
    Implicit Type-Casting in Assignment

    Explicit type-casting is not required if you assign an value to a variable, because there is no loss of precision. The compiler will perform the type-casting automatically (i.e., implicit type-casting). For example,,

    int i = 3; double d; d = i; d = (double) i; double aDouble = 55; double nought = 0;

    The following diagram shows the order of implicit type-casting performed by compiler. The rule is to promote the smaller type to a bigger type to prevent loss of precision, known as widening conversion. Narrowing conversion requires explicit type-cast to inform the compiler that you are aware of the possible loss of precision. Take note that is treated as an 16-bit unsigned integer in the range of . value cannot be type-casted (i.e., converted to non-).

    Example: Suppose that you want to find the average (in ) of the integers between and . Study the following codes:

    1 2 3 4 5 6 7 8 9 10 11 12 13 public class Sum1To100 { public static void main(String[] args) { int sum = 0; double average; int number = 1; while (number <= 100) { sum += number; ++number; } average = sum / 100; System.out.println("Average is " + average); } }

    This is because both the and are . The result of division is an , which is then implicitly casted to and assign to the variable . To get the correct answer, you can do either:

    average = (double)sum / 100; average = sum / (double)100; average = sum / 100.0; average = (double)(sum / 100);

    Compound Assignment Operators

    Besides the usual simple assignment operator () described earlier, Java also provides the so-called compound assignment operators as listed:

    Assign the value of the LHS to the variable at the RHS
    var = exprx = 5;
    +=Compound addition and assignmentvar += expr
    same asvar = var + expr
    x += 5;
    same as x = x + 5
    -=Compound subtraction and assignmentvar -= expr
    same asvar = var - expr
    x -= 5;
    same as x = x - 5
    *=Compound multiplication and assignmentvar *= expr
    same asvar = var * expr
    x *= 5;
    same as x = x * 5
    /=Compound division and assignmentvar /= expr
    same asvar = var / expr
    x /= 5;
    same as x = x / 5
    %=Compound remainder (modulus) and assignmentvar %= expr
    same asvar = var % expr
    x %= 5;
    same as x = x % 5


    Java supports these unary arithmetic operators: increment () and decrement () for all numeric primitive types (, , , , , and , except ).

    ++Increment the value of the variable by 1.
    x++ or ++x is the same as x += 1 or x = x + 1
    int x = 5;
    --Decrement the value of the variable by 1.
    x-- or --x is the same as x -= 1 or x = x - 1
    int y = 6;

    The increment () and decrement () operate on its operand and store the result back to its operand. For example, retrieves x, increment and stores the result back to x. Writing is a logical error!!!

    Unlike other unary operator (such as negate ()) which promotes , and to , the increment and decrement do not promote its operand (because there is no such need).

    The increment/decrement unary operator can be placed before the operand (prefix), or after the operands (postfix), which affects its resultant value.

    • If these operators are used by themselves (e.g., or ), the outcomes are the same for pre- and post-operators, because the resultant values are discarded.
    • If '++' or '--' involves another operation (e.g., or ), then pre- or post-order is important to specify the order of the two operations:
    Increment var, then use the new value of var
    y = ++x;
    same as x=x+1; y=x;
    Use the old value of var, then increment var
    y = x++;
    same as oldX=x; x=x+1; y=oldX;
    --varPre-Decrementy = --x;
    same as x=x-1; y=x;
    var--Post-Decrementy = x--;
    same as oldX=x; x=x-1; y=oldX;

    For examples,

    x = 5; System.out.println(x++); x = 5; System.out.println(++x);

    Prefix operator (e.g, ) could be more efficient than postfix operator (e.g., )?!

    Relational and Logical Operators

    Very often, you need to compare two values before deciding on the action to be taken, e.g. if mark is more than or equals to 50, print "PASS!".

    Java provides six comparison operators (or relational operators):

    OperatorDescriptionUsageExample (x=5, y=8)
    ==Equal toexpr1 == expr2(x == y) → false
    !=Not Equal toexpr1 != expr2(x != y) → true
    >Greater thanexpr1 > expr2(x > y) → false
    >=Greater than or equal toexpr1 >= expr2(x >= 5) → true
    <Less thanexpr1 < expr2(y < 8) → false
    <=Less than or equal toexpr1 >= expr2(y <= 8) → true

    In Java, these comparison operations returns a value of either or .

    Each comparison operation involves two operands, e.g., . It is invalid to write in programming. Instead, you need to break out the two comparison operations , , and join with with a logical AND operator, i.e., , where denotes AND operator.

    Java provides four logical operators, which operate on operands only, in descending order of precedences, as follows:

    !Logical NOT!booleanExpr
    ^Logical XORbooleanExpr1 ^ booleanExpr2
    &&Logical ANDbooleanExpr1 && booleanExpr2
    ||Logical ORbooleanExpr1 || booleanExpr2

    The truth tables are as follows:

    AND (&&)truefalse

    OR (||)truefalse

    NOT (!)truefalse

    XOR (^)truefalse


    (x >= 0) && (x <= 100)   (x < 0) || (x > 100) !((x >= 0) && (x <= 100))   ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0)

    Exercise: Study the following program, and explain its output.

    public class RelationalLogicalOpTest { public static void main(String[] args) { int age = 18; double weight = 71.23; int height = 191; boolean married = false; boolean attached = false; char gender = 'm'; System.out.println(!married && !attached && (gender == 'm')); System.out.println(married && (gender == 'f')); System.out.println((height >= 180) && (weight >= 65) && (weight <= 80)); System.out.println((height >= 180) || (weight >= 90)); } }

    Write an expression for all unmarried male, age between 21 and 35, with height above 180, and weight between 70 and 80.

    Exercise: Given the year, month (1-12), and day (1-31), write a boolean expression which returns true for dates before October 15, 1582 (Gregorian calendar cut over date).


    Operator Precedence

    The precedence from highest to lowest is: (unary), , , '. But when in doubt, use parentheses!

    System.out.println(true || true && false); System.out.println(true || (true && false)); System.out.println((true || true) && false); System.out.println(false && true ^ true); System.out.println(false && (true ^ true)); System.out.println((false && true) ^ true);
    Short-Circuit Operation

    The logical AND () and OR () operators are known as short-circuit operators, meaning that the right operand will not be evaluated if the result can be determined by the left operand. For example, gives ; give without evaluating the right operand. This may have adverse consequences if you rely on the right operand to perform certain operations, e.g. but will not be evaluated.


    A is a sequence of characters. A string literal is surrounded by a pair of double quotes, e.g.,

    String s1 = "Hi, This is a string!" String s2 = ""

    You need to use an escape sequence for special control characters (such as newline and tab ), double-quote and backslash (due to conflict) and Unicode character (if your editor does not support Unicode input), e.g.,

    String s3 = "A \"string\" nested \\inside\\ a string" String s4 = "Hello, \u60a8\u597d!"

    Single-quote () does not require an escape sign.

    String s5 = "Hi, I'm a string!"

    String and '+' Operator

    In Java, is a special operator. It is overloaded. Overloading means that it carries out different operations depending on the types of its two operands.

    • If both operands are numbers (, , , , , , ), performs the usual addition, e.g., 1 + 2 → 3 1.2 + 2.2 → 3.4 1 + 2.2 → 1.0 + 2.2 → 3.2
    • If both operands are s, concatenates the two Strings and returns the concatenated . E.g., "Hello" + "world" → "Helloworld" "Hi" + ", " + "world" + "!" → "Hi, world!"
    • If one of the operand is a and the other is numeric, the numeric operand will be converted to and the two s concatenated, e.g., "The number is " + 5 → "The number is " + "5" → "The number is 5" "The average is " + average + "!" (suppose average=5.5) → "The average is " + "5.5" + "!" → "The average is 5.5!" "How about " + a + b (suppose a=1, b=1) → "How about 11"

    String Operations

    The most commonly-used methods are:

    • : return the length of the string.
    • : return the at the position (index begins at to ).
    • : for comparing the contents of two strings. Take note that you cannot use to compare two strings.

    For examples,

    String str = "Java is cool!"; System.out.println(str.length()); System.out.println(str.charAt(2)); System.out.println(str.charAt(5));   String anotherStr = "Java is COOL!"; System.out.println(str.equals(anotherStr)); System.out.println(str.equalsIgnoreCase(anotherStr)); System.out.println(anotherStr.equals(str)); System.out.println(anotherStr.equalsIgnoreCase(str));

    To check all the available methods for , open JDK API documentation ⇒ select package "" ⇒ select class "" ⇒ choose method. For examples,

    String str = "Java is cool!"; System.out.println(str.length()); System.out.println(str.charAt(2)); System.out.println(str.substring(0, 3)); System.out.println(str.indexOf('a')); System.out.println(str.lastIndexOf('a')); System.out.println(str.endsWith("cool!")); System.out.println(str.toUpperCase()); System.out.println(str.toLowerCase());

    String/Primitive Conversion

    "String" to "int/byte/short/long": You could use the JDK built-in methods to convert a containing a valid integer literal (e.g., "") into an (e.g., ). The runtime triggers a if the input string does not contain a valid integer literal (e.g., ""). For example,

    String inStr = "5566"; int number = Integer.parseInt(inStr); number = Integer.parseInt("abc");

    Similarly, you could use methods , , to convert a string containing a valid , or literal to the primitive type.

    "String" to "double/float": You could use or to convert a (containing a floating-point literal) into a or , e.g.

    String inStr = "55.66"; float aFloat = Float.parseFloat(inStr); double aDouble = Double.parseDouble("1.2345"); aDouble = Double.parseDouble("abc");

    "String" to "char": You can use to extract individual character from a , e.g.,

    String msg = "101100111001!"; int pos = 0; while (pos < msg.length()) { char binChar = msg.charAt(pos); ....... ++pos; }

    "String" to "boolean": You can use method to convert string of "" or "" to or , e.g.,

    String boolStr = "true"; boolean done = Boolean.parseBoolean(boolStr); boolean valid = Boolean.parseBoolean("false");

    Primitive (int/double/float/byte/short/long/char/boolean) to "String": To convert a primitive to a , you can use the '+' operator to concatenate the primitive with an empty, or use the JDK built-in methods , , , , , etc. For example,

    String s1 = 123 + ""; String s2 = 12.34 + ""; String s3 = 'c' + ""; String s4 = true + ""; String s1 = String.valueOf(12345); String s2 = String.valueof(true); double d = 55.66; String s3 = String.valueOf(d); String s4 = Integer.toString(1234); String s5 = Double.toString(1.23); char c1 = Character.toString('z'); char c = 'a'; String s5 = c; String s6 = c + ""; boolean done = false; String s7 = done + ""; String s8 = Boolean.toString(done); String s9 = String.valueOf(done);

    "char" to "int": You can convert char to to to by subtracting the with (e.g., ).

    Flow Control

    There are three basic flow control constructs - sequential, conditional (or decision), and loop (or iteration), as illustrated below.

    Sequential Flow Control

    A program is a sequence of instructions executing one after another in a predictable manner. Sequential flow is the most common and straight-forward, where programming statements are executed in the order that they are written - from top to bottom in a sequential manner.

    Conditional Flow Control

    There are a few types of conditionals, if-then, if-then-else, nested-if (if-elseif-elseif-...-else), switch-case, and conditional expression.

    Braces: You could omit the braces , if there is only one statement inside the block. However, I recommend that you keep the braces to improve the readability of your program. For example,

    if (mark >= 50) System.out.println("PASS"); else { System.out.println("FAIL"); System.out.println("Try Harder!"); }

    "switch-case" is an alternative to the "nested-if". In a switch-case statement, a statement is needed for each of the cases. If is missing, execution will flow through the following case. You can use an , , , or variable as the case-selector, but NOT , , and . (JDK 1.7 supports as the case-selector).

    Conditional Operator (? :)

    A conditional operator is a ternary (3-operand) operator, in the form of . Depending on the , it evaluates and returns the value of or .

    booleanExpr?trueExpr:falseExprSystem.out.println((mark >= 50) ? "PASS" : "FAIL"); max = (a > b) ? a : b; abs = (a > 0) ? a : -a;

    Exercises on Conditional


    Loop Flow Control

    Again, there are a few types of loops: for, while-do, and do-while.

    for (initialization;test;post-processing) {body;}   int sum = 0; for (int number = 1; number <= 1000; ++number) { sum += number; }
    while (test) {body; }  

    Sports Production Camera
    House of Worship



    WAYNE, NJ (August 1, 2017)JVC Professional Video, a division of JVCKENWOOD USA Corporation, today announced a free firmware upgrade for its 4KCAM GY HM200SP sports production camcorder and GY-HM200HW house of worship camcorder that allows full-screen graphic overlays. Designed for enhanced single-camera productions, both cameras already feature on-board customized, lower-third titling solutions for recorded or streamed HD video output that does not require the use of an external CG or production switcher.

    Users can add up to 50 .JPG or .PNG graphics via an SD card and store them in the camera. Graphics can be advanced manually or presented as a slideshow. A graphics loop is activated using the camera’s web interface, with slideshow timing allowing up to 99 seconds per graphic (0 = manual advance) set by the user.

    With the new full-screen graphics, GY-HM200SP users can create slideshows that present advertising during halftime or other extended breaks in the action. For worship applications, graphics can display scripture readings or lyrics, with the operator manually advancing graphics as the service progresses.

    Graphics can be produced with PowerPoint or any photo editing software and saved as a series of .PNG files with alpha (transparency) channel, which provides the most flexibility for creating overlays. For example, full-screen graphics can be used concurrently with the GY-HM200SP’s score panel graphics, allowing advertising or promotional banners to be placed on the screen throughout a game. Full-screen graphics are saved at 960x540 and upscaled to 1920x1080.

    The firmware upgrade also adds hockey and soccer-specific scoring for the GY-HM200SP and the ability to position score overlays in various screen positions. An earlier firmware upgrade released in January added baseball and basketball overlays, as well as the ability to upload team logos and custom characters.

    Beyond integrated graphics, the GY-HM200SP and GY-HM200HW offer all the professional features of the GY-HM200, including a 1/2.3-inch BSI CMOS imager, integrated 12x zoom lens with optical image stabilizer, and 24x dynamic zoom in HD mode. The cameras record 4K, HD, and SD footage in a variety of file formats to economical Class 10 SDHC/SDXC memory cards. The built-in HD streaming engine with Wi-Fi and 4G LTE connectivity provides live access to CDNs like JVC VIDEOCLOUD, Facebook Live, and YouTube. Other features include dual XLR audio inputs, integrated handle with hot shoe and dedicated microphone mount, and SDI and HDMI video outputs.

    Headquartered in Wayne, New Jersey, JVC Professional Video is a division of JVCKENWOOD USA Corporation, a wholly-owned subsidiary of JVCKENWOOD Corporation. The company is a leading manufacturer and distributor of broadcast and professional video equipment, as well as D-ILA front projection systems. For more information, visit JVC’s website at or call (800) 582 5825.

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