Java Day-1

© People Strategists - Duplication is strictly prohibited -www.peoplestrategists.com

1

Day 1Introduction to Java

Data Types And VariablesOperators And Expressions

Control Flow Statement

© People Strategists - Duplication is strictly prohibited -www.peoplestrategists.com 2

Introduction to Java


Introduction

• The first version of Java was introduced in 1991.• Java was initially called as Oak.• In 1995, Oak was renamed to Java.• Java programming language is platform-independent and object-

oriented.


Installation

• Java software can be downloaded from the following site:• http://www.oracle.com/technetwork/java/javase/downloads/index.html

• Run the executable file and install Java.


Environment Setup

• The following two environment variables need to be set:• PATH• CLASSPATH

• The PATH environment variable specifies a set of directories whereexecutable programs are located.

• The PATH environment variable is set to the bin folder of JDKinstallation.


Environment Setup (Contd.)

• The CLASSPATH environment variable specifies the class path on agiven system.

• A class path is a list of locations that are searched for classes whenthe Java Virtual Machine attempts to locate a referenced class.

• The CLASSPATH must include the current directory in order to runJava programs from the command line with the java command.

• The Classpath environment variable is set to the class files folder ofJava program.



• The environment variables are set using the System Properties dialogbox.

• To open the System Properties dialog box following steps should beperformed:

• Control PanelAll Control Panel Items System Advanced systemsettings



• The System Properties dialog box will be display as shown in thefollowing figure.


JVM, JRE, JDK

• JVM stands for Java Virtual Machine.• The JVM provides a platform-independent way of executing Java

code.• In Java, the Java complier translates the Java source code into an

intermediate code know as byte code.• The JVM interprets the byte code into the machine code depending

upon the underlying operating system and hardware combination.


JVM, JRE, JDK

• The execution flow of a Java program.

Java ProgramJava Program Java CompilerJava Compiler BytecodeBytecode Java InterpreterJava Interpreter Real MachineReal Machine


JVM, JRE, JDK (Contd.)

• JRE stands for Java Runtime Environment.• JRE contains JVM, class libraries, and other supporting files.• If you want to run any java program, you need to have JRE installed in

the system.• The JVM runs the Java program using the class libraries and other

supporting files provided in JRE.



• JDK stands for Java Development Kit.• JDK contains tools to develop and run Java program.• The various components of JDK are:

• Java Compiler• Java Interpreter• Java Disassembler• Java Header File Generator• Java Documentation• Java Debugger• Java Applet Viewer• JRE




Java Programming Basics

• Java programming language allows to create following application• Stand-alone Java application• Java Applet application

• A stand-alone Java application are CUI or GUI based application thatrun on a stand-alone computer.

• A Java Applet application are small internet application that run on abrowser.


Java Programming Basics (Contd.)

• A structure of Java program may contain one or more sections asshown in the following list:

• Documentation• Package• Import• Interface• Class• Main Method


A First Java Program

• An example for defining a simple Java program:public class Demo {

public static void main(String args[]){System.out.println("My First Java Program");

}}


Compiling and executing Java Applications

• Compiling Java program• The javac command is used to compile a Java program.

• javac Demo.java

• Executing Java program• The java command is used to execute a Java program.

• java Demo


Java Source Files

• The following are the rules associated with declaring classes, importstatements, and package statements in a source file:

• There can be only one public class per source file.• If there is a public class in a file, then, the filename must match the class

name.• If the class is part of a package, the package statement must be the first line in

the code.• The import statements must lie between the package statement and the class

definition statement.• The package and import statements apply to all classes within the source

code file.• A source file can have more that one nonpublic class.


The JDK Directory Structure

includeinclude

JDKJDK

binbin liblib jrejre src.zipsrc.zip dbdb

binbin liblib

clientclient serverserver extext securitysecurity appletsapplets serverserver


Data Types And Variables


Identifiers

• Identifiers are the names used to identify various Java items, such asa variable, class, method, interface, and package.

• Identifiers allows a programmer to refer to these item from otherplaces in the code.

• While name an identifier following rules must be followed:• Must start with a letter or currency character, $, or underscore, _.• After the first character, identifier can contain combination of letters,

currency character, underscore, or numbers.• The Java keywords can not be used as identifiers.• Identifiers are case-sensitive.


Identifiers (contd.)

• The standard Java naming conventions are:• Packages names should be in lowercase.• Classes and interfaces names should be in camel case.• Methods and variable names should be in mixed case.• Constants names should be in uppercase.


Identifiers (contd.)

• Example:

package testinterface PrintableIntf{…}class PaperDemo{int paperSize;double final MIN_THICKNESS=0.1;void displayData(){…}}


Primitive Datatypes

• The primitive datatypes in Java are:

• Note: To work with string data Java provides, String class and the default value is null.

Data type Description Default value

char 16 bits Unicode character data \u0000'

boolean boolean values true or false false

byte 8 bits signed integer 0

short 16 bits signed integer 0

int 32 bits signed integer 0

long 64 bits signed integer 0L

float 32 bits signed floating point number 0.0f

double 64 bits signed floating point number 0.0d


Primitive Datatypes (Contd.)

• The range of numeric primitive data types:

• The boolean data type does not has any range.• The char data type range is 0 to 216. That is it can hold data from

0 to 65535.

Data type BitsAllocated Min Range Max Range

byte 8 -27 27-1

short 16 -215 215-1

int 32 -231 231-1

long 64 -263 263-1

float 32 n/a n/adouble 64 n/a n/a


Primitive Variables Declaration andInitialization• Java provides containers called variables to store data within a

program.• To declare a primitive variables a combination of a datatype and

identifier is used.• The syntax to declare primitive variable:

<datatype> <identifier>;

• An example to declare primitive variable :int val;


Primitive Variables Declaration andInitialization (Contd.)• After declaring a primitive variable, a value can be assigned.• The process of assigning values to a variable is called initialization.• The syntax to initialize a primitive variable:

<variable name>=<value>;

• An example to initialize a primitive variable :int val;val=10;

• The declaration and initialization of primitive variable can be done ina single line as shown in the following code:int val=10;


Literals

• A literal is constant value.• Literals are commonly used to initialize a variable.• Different types of literals are:

• Integer• Floating• Boolean• Character• String


Literals (Contd.)

• The integer literal are used to represent integer numbers.• An integer literal is of type long if it ends with the letter L or l else it is

of type int.• The integer literals can be represented using the following number

system:• Decimal• Binary• Octal• Hexadecimal

• Decimal number system consists of digits from 0 to 9.• Example: int a=30;


Literals (Contd.)

• Binary number system consists of the digits 0 and 1.• Example: int a=0b11110;

• Octal number system consists of digits from 0 to 7. Therefore, torepresent octal integer, a zero is placed before the number.

• A octal number can include 21 digits excluding the zero• Example: int a=036;• Here, a is holding the value, 30.


Literals (Contd.)

• Hexadecimal number system consists of digits from 0 to 9 and the lettersfrom A to F.

• Example: int a=0x1E;• Here, a is holding the value, 30.

• The floating literals are used to represent fractional number.• A floating-point literal is of type float if it ends with the letter F or f; else its

type is double.• Example: float fValue=45.8f;

double dValue=45.8;double dValE=1.234e2;float fValE=1.234e2f;

• Here, dValE and fValE are using scientific notation.


Literals (Contd.)

• In numeric literals, integer and floating any number of underscorecharacters (_) can appear anywhere between digit.

• This feature enables to separate groups of digits in numeric literals toimprove the readability.

• Example:int iVal=1_999;

float fVal=1_999.11_1f;

• Boolean literals are used to represent boolean values.• The boolean values are true and false

• Example: boolean boolVal=true;


Literals (Contd.)

• Character literals are used to represent characters.• The character literals are enclosed in single quotes.• Character literals can also be represented using the Unicode

notification.• Example: char cVal='a';

char cValU='\u004E';• Here, the cValU is holding the letter, N.

• String literals are used to represent string data.• String literals are enclosed in double quotes.

• Example: String sVal="Hello";


Literals (Contd.)

• An example to work with literals:public class LiteralsDemo {

public static void main(String[] argv) {int decimal=30;int binary=0b11110;int octal=036;int hexadecimal=0x1E;float fValue=45.8f;double dValue=45.8;

double dValE=1.234e2;

float fValE=1.234e2f;


Literals (Contd.)

int iVal=1_999;

float fVal=1_999.11_1f;

boolean boolVal=true;

char cVal='a';

char cValU='\u004E';

String sVal="Hello";

System.out.println(decimal+", "+binary+", "+octal+", "+

fValue+", "+dValue+", "+dValE+", "+fValE+", "+iVal+","+fVal+", "+

boolVal+", "+cVal+", "+cValU+", "+sVal);

}

}


Literals (Contd.)

• The preceding code output will be:30, 30, 30, 45.8, 45.8, 123.4, 123.4, 1999, 1999.111,true, a, N, Hello


Arrays

• An array is a collection of data storage location that can holds onlysame type of data.

• The data stored in an array is called element.• Each element in an array is stored at a specific index.• An array can be of any type and can have one or more dimensions.• The dimension of an array is determined by the number of indexes

needed to identify an element.• The commonly used array dimensions are:

• One-dimensional array• Two-dimensional array


Arrays (Contd.)

• One dimensional array is represented with single index.• The syntax to declare one-dimensional array:

<array_type> <array_name>[];

• The syntax to create one-dimensional array:<array_name>=new <array_type>[size];

• An example to create one-dimensional array:int rollNo[];rollNo=new int[5];Orint rollNo[]=new int[5];


Arrays (Contd.)

• The following figure shows the elements position in a one-dimensional array:

1st element 5th element

rollNo


Arrays (Contd.)

• The syntax to initialize one-dimensional array:<array_name>[index_no]=value;or<array_type> <array_name>[]={array_element1,..,array_element n}

• An example to initialize one-dimensional array:rollNo[0]=111;……………rollNo[4]=115;

Orint rollNo[]={111,112,113,114,115};


Arrays (Contd.)

• The following figure shows the data stored in a one-dimensionalarray:

111 112 113 114 115

Elements

0th

index1st

index2nd

index3rd

index4th

index

rollNo


Arrays (Contd.)

• An example to work with one-dimensional array:public class Demo {

public static void main(String args[]){int rollNo[]={111,112,113,114,115};System.out.println(rollNo[3]);

}}


Arrays (Contd.)

• Two dimensional array is represented with two indexes.• The syntax to declare two-dimensional array:

<array_type> <array_name>[][];

• The syntax to create two-dimensional array:<array_name>=new <array_type>[row_size][col_size];

• An example to create two-dimensional array:int pointCord[][];pointCord =new int[3][2];Orint pointCord[][]=new int[3][2];


Arrays (Contd.)

• The following figure shows the elements position in two-dimensionalarray:

1st row2nd row3rd row

1st column 2nd column


Arrays (Contd.)

• The syntax to initialize two-dimensional array:<array_name>[row_index][col_index]=value;

or<array_type> <array_name>[][]={{row0col0_element,…,row0coln_element} ,.., {rowncol0_element,..,rowncoln_element} }

• An example to initialize two-dimensional array:pointCord[0][0]=5;……………pointCord[2][1]=4;

Or

int pointCord [][]={{5,3},{4,3},{2,8}};


Arrays (Contd.)

• The following figure shows the data stored in two-dimensional array.

5 34 32 8

[rowindex0][colindex0][rowindex1][colindex0][rowindex2][colindex0]

[rowindex0][colindex1][rowindex1][colindex1][rowindex2][colindex1]


Arrays (Contd.)

• An example to work with two-dimensional array:public class Demo {

public static void main(String args[]){int pointCord[][]={{5,3},{4,3},{2,8}};System.out.println(pointCord[2][1]);

}}


Operators And Expressions


Expression

• An expression is a syntactic construction that has a value.• Expressions are formed by combining operands and operators, which

returns a value.• An example of expression:

a+b• Here a and b are operands and + is the operator.


Operators

• Operators are special symbols that perform specific operations onone, two, or three operands, and then return a result.

• The different types of operators are:• Arithmetic Operators• Assignment Operator• Relational Operators• Logical Operators• Increment and Decrement Operators• The Conditional Operator


Assignment Operator

• An assignment operator,=, is used to assign a value.• The assignment operator is evaluated from right to left.• An example to use assignment operator:

a = b = c = 0;The preceding statement would assign 0 to c, then c to b then b to a.


Arithmetic Operators• The arithmetic operators are used to perform arithmetic operations,

such as addition, subtraction, multiplication, and division.• The following tables shows the arithmetic operators, its description,

and its usage:Operator Description Example

Assume integer variable a holds 10 and variableb holds 20

+ Addition - Adds values on either side of the operator a + b will give 30

- Subtraction - Subtracts right hand operand from left handoperand

a - b will give -10

* Multiplication - Multiplies values on either side of the operator a * b will give 200

/ Division - Divides left hand operand by right hand operand a / b will give 2

% Modulus - Divides left hand operand by right hand operand andreturns remainder

b % a will give 0


Arithmetic Compound Assignment Operators

• Java allows you to combine the arithmetic and assignment operatoras shown in the following table:

Operator Description+= Addition assignment-= Subtraction assignment*= Multiplication assignment/= Division assignment%= Modulus assignment


Arithmetic Compound Assignment Operators(Contd.)• An example to work with arithmetic operators:

a=10b=20b=a+b

• The preceding code snippet can be otherwise written as:a=10b+=a;


Relational Operators• Relational operators determine the relationship that one operand has

to other.• The following tables shows the relational operators its description,

and its usage:

Operator Description ExampleAssume integer variable a holds 10 and variable bholds 20

== Checks if the values of two operands are equal or not, if yes then conditionbecomes true.

(a == b)is not true

!= Checks if the values of two operands are equal or not, if values are not equalthen condition becomes true.

(a != b)is true

> Checks if the value of left operand is greater than the value of right operand,if yes then condition becomes true.

(a > b)is not true

< Checks if the value of left operand is less than the value of right operand, ifyes then condition becomes true.

(a < b)is true

>= Checks if the value of left operand is greater than or equal to the value ofright operand, if yes then condition becomes true.

(a >= b)is not true

<= Checks if the value of left operand is less than or equal to the value of rightoperand, if yes then condition becomes true.

(a <= b)is true


Increment and Decrement Operators

• The increment operator, ++, increases its operands value by one.• The decrement operator, --, decreases its operands value by one.• The increment and decrement operator of two types:

• Prefix• Postfix

• In prefix increment or decrement operator, the operator ++ or –precedes the operand. Example: ++a or --a

• In postfix increment or decrement operator, the operator ++ or –follows the operand. Example: a++ or b++


Increment and Decrement Operators (Contd.)

• An example to work with prefix increment operator:public class Demo {

public static void main(String args[]){int a=1;int b=++a;System.out.println("a="+a);System.out.println("b="+b);

}}

• The preceding code will generate the output:a=2b=2


Increment and Decrement Operators (Contd.)

• An example to work with postfix increment operator:public class Demo {

public static void main(String args[]){int a=1;int b=a++;System.out.println("a="+a);System.out.println("b="+b);

}}

• The preceding code will generate the output:a=2b=1


Logical Operators

• The logical operators operates on boolean operand.• The following tables shows the logical operators its description, and

its usage:Operator Description Example

Assume Boolean variables a holdstrue and variable b holds false

&& Called Logical AND operator. If both the operandshold true value, then the condition becomes true.

(a && b) is false.

|| Called Logical OR Operator. If any of the two operandshold true value, then the condition becomes true.

(a || b) is true.

! Called Logical NOT Operator. Use to reverses thelogical state of its operand. If a condition is true thenLogical NOT operator will make false.

!(a && b) is true.


Conditional Operator

• The conditional operator,?:, is used to create a simple conditionalexpression.

• An example to work with conditional operator:public class Demo {

public static void main(String args[]){int a=10;int b=20;int max=a>b?a:b;System.out.println("max="+max);

}}

• The preceding code will display the output:max=20


Operator Precedence

• The precedence of operators is shown in the following table:Operators Precedence

postfix expr++ expr--

unary ++expr --expr +expr -expr ~ !

multiplicative * / %

additive + -

shift << >> >>>

relational < > <= >= instanceof

equality == !=

bitwise AND &

bitwise exclusive OR ^

bitwise inclusive OR |

logical AND &&

logical OR ||

ternary ? :

assignment = += -= *= /= %= &= ^= |= <<= >>= >>>=© People Strategists - Duplication is strictly prohibited -www.peoplestrategists.com 62

Operator Precedence (Contd.)

• The closer to the top of the table an operator appears, the higher itsprecedence.

• Operators with higher precedence are evaluated before operatorswith relatively lower precedence.

• Operators on the same line have equal precedence.• When operators of equal precedence appear in the same expression,

a rule must govern which is evaluated first.• All binary operators except for the assignment operators are

evaluated from left to right; assignment operators are evaluated rightto left.


Type Casting

• Type casting is the process of converting an entity of one data typeinto another data type.

• The different type casting supported by Java are:• Implicit type casting• Explicit type casting

• In implicit type casting, one type of data is assigned to another typeof variable.

• An example of implicit type casting:int a=10;long b=a;


Type Casting (Contd.)

• Implicit type casting will take place in two condition:• The two types must be compatible.• The destination type must be larger than the source type.

• In explicit type casting, a larger data type value is converted andstored in smaller data type variable.

• An example of explicit type casting:long a=10;int b=(int)a;



• Consider the following code snippet:float fVal=100.56f;int iVal=(int)fVal;

• In the preceding code snippet, iVal, will have the value,100. This isbecause an integer variable can not store a decimal value. Therefore,the digit after the decimal part is lost.

• Consider the following code snippet:int iVal= 150;byte bVal=(byte)iVal;

• In the preceding code snippet, bVal, will have the value, -106.© People Strategists - Duplication is strictly prohibited -

www.peoplestrategists.com 66


• This is byte variable can hold numbers between the range -128 to127.

• The 16 bit binary representation of 150 is:0000000010010110

• When the 8 bits are lost from 16 bit, the value is:10010110

In a eight bit representation, the left most is the sign bit. Here, the leftmost bit is 1, which mean negative value. Therefore, the bVal holds thevalue -106


Control Flow Statements


Statements

• Statements contain the instructions to execute by the complier.• Control statements enable us to specify the order in which the

various instructions in a program are to be executed by the computer.• Control statements determine the flow of control in a program.• Different types of control statements in Java are:

• Conditional Construct Control Statement• Repetition or Loop Construct Control Statement


Conditional Construct Control Statement

• The conditional construct control statements allow a program toexecute a certain piece of code based on a decision.

• The different types of conditional construct control statements are:• if construct• if-else construct• switch construct


if Construct

• The different types of conditional cotro• The if construct tells the program to execute a certain section of code

only if a particular test evaluates to true.• The syntax to work with if construct :

if (condition)statement1;

• In the preceding syntax,• Each statement may be a single statement or a compound statement

enclosed in curly braces (a block).• The condition is any expression that returns a boolean value.


if Construct (Contd.)

• The if construct example:char option='y';

if(option == 'y'){System.out.println("If block executed");

}System.out.println("After if block");

• The output of the preceding code snippet will be:If block executedAfter if block


if Construct (Contd.)

• An if statement can be the target of another if or else statement andis known as nested if.

• The nested if construct example:int a=12;if(a>=10){if(a<=20)System.out.println("value of a is in range: 10 to 20");}

• The output of the preceding code snippet will be:value of a is in range: 10 to 20


if-else Construct

• The if-else construct is Java’s conditional branch statement that canbe used to route program execution through two different paths.

• The syntax to work with if-else construct :if (condition) statement1;else statement2;

• In the preceding syntax,• Each statement may be a single statement or a compound statement

enclosed in curly braces (a block).• The condition is any expression that returns a boolean value.• The else clause is optional.


if-else Construct (Contd.)

• The if…else construct example:int a=1;int b=5;if(a>b)

System.out.println(a+" is greater than "+b);else

System.out.println(b+" is greater than "+a);

• The output of the preceding code snippet will be:5 is greater than 1



• A common programming construct that is based upon a sequence ofnested ifs is the if-else-if ladder.

• The syntax to work with if-else-if ladder construct:if (condition)statement;else if (condition)statement;else if (condition)statement;…elsestatement;



• The if-else-if ladder construct example:int month = 4; // AprilString season;if(month == 12 || month == 1 || month == 2)season = "Winter";else if(month == 3 || month == 4 || month == 5)season = "Spring";else if(month == 6 || month == 7 || month == 8)season = "Summer";else if(month == 9 || month == 10 || month == 11)season = "Autumn";elseseason = "Bogus Month";System.out.println("April is in the " + season + ".");



• The output of the preceding code snippet will be:

April is in the Spring.


Switch Construct

• The switch statement is Java’s multi way branch statement.• It provides an easy way to dispatch execution to different parts of

code based on the value of expression.• It often provides a better alternative than a large series of if-else-if

statements.


Switch Construct (Contd.)

• The syntax to work with switch construct:switch (expression) {case value1:// statement sequencebreak;case value2:// statement sequencebreak;…case valueN:// statement sequencebreak;default:// default statement sequence}



• The expression must be of type byte, short, int, or char.• Each of the values specified in the case statements must be of a type

compatible with the expression.• Each case value must be a unique literal .• Duplicate case values are not allowed.



• The switch construct example:class SampleSwitch {public static void main(String args[]) {for(int i=0; i<6; i++)switch(i) {case 0:System.out.println("i is zero.");break;case 1:System.out.println("i is one.");break;



case 2:System.out.println("i is two.");break;case 3:System.out.println("i is three.");break;default:System.out.println("i is greater than 3.");}}}



• The output of the preceding code will be:

i is zero.i is one.i is two.i is three.i is greater than 3.i is greater than 3.



• Consider the following code:public class SwitchDemo {

public static void main(String args[]){char cVal='a';switch(cVal){case 'a':case 'e':case 'i':case 'o':



case 'u':System.out.println("Vowles");break;

default:System.out.println("Consonant");break;

}}

}

• The preceding code output will be:Vowles



• In the preceding code, if the break statement after the statement,System.out.println("Vowles");, is removed the output will be:Vowles

Consonant


Loop Construct Control Statement

• The loop construct control statements allow to repeat a block of codemultiple times, while the given condition is true.

• The different types of loop construct control statements are:• while loop construct• do-while loop construct• for loop construct


while Loop Construct

• The while loop is Java’s most fundamental loop statement.• It repeats a statement or block while its controlling expression is true.• The syntax to work with while loop:

while(condition) {// body of loop}

• The condition can be any Boolean expression.• The body of the loop will be executed as long as the conditional

expression is true.• When condition becomes false, control passes to the next line of code

immediately following the loop.


while Loop Construct (Contd.)

• The while loop construct example:int i = 4;while(i > 0) {System.out.println("value " + i);i--;

• The output of the preceding code snippet will be:value 4value 2value 2value 1



• An example of nested while loop:public class WhileLoopDemo {public static void main(String args[]){

{int i = 1, j = 1;while (i <= 2){



while (j <= 10) {

System.out.println(i + " * " + j + " = " + (i * j));

j++;

}

i++;

System.out.println("");

System.out.println("");

}

}

}

} © People Strategists - Duplication is strictly prohibited -www.peoplestrategists.com 92


• The preceding code output will be:1 * 1 = 11 * 2 = 21 * 3 = 31 * 4 = 41 * 5 = 51 * 6 = 61 * 7 = 71 * 8 = 81 * 9 = 91 * 10 = 10


do-while Loop Construct

• When the condition in a while loop is found false for the first time,the body of the loop is not executed at all.

• At times, you need to execute the body of the loop at least once. Javasupplies a loop that does just that: the do-while loop.

• The do-while loop always executes its body at least once, because itsconditional expression is at the bottom of the loop.

• The syntax to work with do-while construct:do {// body of loop} while (condition);


do-while Loop Construct (Contd.)

• The do-while construct example:

int n = 0;do {System.out.println("value " + n);n--;} while(n > 0);

• The output of the preceding code snippet will be:value 0



• An example of nested while loop:public class DoWhileDemo {

public static void main(String args[]) {int i = 1, j;do {

j=1;do {

System.out.print(i + " ");j++;

} while (j <= i);



System.out.println("");i++;

} while (i <= 5);

}}

• The preceding code output will be:12 23 3 34 4 4 45 5 5 5 5


for Loop Construct

• Similar to while and do-while, for loop is used to execute a set of statements.• The syntax to work with for loop:

for(initialization; condition; iteration) {// body}

• When the loop first starts, the initialization portion of the loop is executed.• Then, condition is evaluated.• If this expression is true, then the body of the loop is executed. If it is false, the

loop terminates.• Then, the iteration portion of the loop is executed.• This process repeats until the controlling expression is false.


for Loop Construct (Contd.)

• The for loop construct example:

for(int n=1; n<5; n++)System.out.println("tick " + n);

• The output of the preceding code snippet will be:tick 1

tick 2tick 3tick 4



• An example of nested for loop construct example:int i, j;for(i=0; i<5; i++) {for(j=i; j<5; j++)System.out.print("*");System.out.println();}

• The output of the preceding code snippet will be:***************



• To create an endless for loop following code snippet is used:for(; ;)

• An example to demonstrate a for loop with multiple variables:public class ForLoopDemo {

public static void main(String args[]){for(int x=1,y=10;(x<10)&& (y>1);x++,y--){

System.out.println("x="+x+" y="+y);}

}}



• The preceding code output will be:x=1 y=10x=2 y=9x=3 y=8x=4 y=7x=5 y=6x=6 y=5x=7 y=4x=8 y=3x=9 y=2


Enhanced For Loop Construct

• The enhanced for loop construct is designed to cycle through a collectionof objects, such as an array, in strictly sequential fashion, from start tofinish.

• The enhanced for loop construct of for is also referred to as for-eachconstruct

• The syntax to work with enhanced for loop:for(type itr-var : collection)statement-block

• Type specifies the type and itr-var specifies the name of an iterationvariable that will receive the elements from a collection, one at a time,from beginning to end.

• The collection being cycled through is specified by collection.


Enhanced For Loop (Contd.)

• The enhanced for loop construct example:int nums[] = { 1, 2, 3, 4, 5 };int sum = 0;for(int x: nums){System.out.println("Value is: " + x);sum += x;}System.out.println("Summation: " + sum);

• The output of the preceding code snippet will be:Value is: 1Value is: 2Value is: 3Value is: 4Value is: 5Summation: 15


The Continue Statement

• At times, you need to force an early iteration of a loop.• You might want to continue running the loop but stop processing the

remainder of the code in its body for this particular iteration. The continuestatement performs such an action.

• By default in while and do-while loops, a continue statement causes controlto be transferred directly to the conditional expression that controls theloop.

• By default in a for loop, control goes first to the iteration portion of the forstatement and then to the conditional expression.

• The default transfer of the control can be modified by using a labeledcontinue statement.


The Continue Statement (Contd.)

• The continue statement example:for(int i=0; i<10; i++) {System.out.print(i + " ");if (i%2 == 0) continue;System.out.println("");}

• The output of the preceding code snippet will be:0 12 34 56 78 9



• Java• An example to work with labeled continue statement:

public class LabeledContinueDemo {public static void main(String args[]) {

Outer:for (int i = 0; i < 2; i++) {

inner:for (int j = 0; j < 2; j++) {

System.out.println("InnerFor Loop");



continue Outer;}

System.out.println("Outer For Loop");}

System.out.println("Loop Ended");}

}

• The preceding code output will be:Inner For LoopInner For LoopLoop Ended


The Break Statement

• We often come across situations where we want to jump out of aloop instantly, without waiting to get back to the conditional test.

• The keyword break allows us to do this.• When break is encountered inside any loop, control automatically

passes to the first statement after the loop.• The labeled break statement can be used to exit out of the labeled

loop.


The Break Statement (Contd.)

• An example to work with labeled break statement:public class LabeledBreakDemo {

public static void main(String args[]) {Outer:

for (int i = 0; i < 2; i++) {inner:

for (int j = 0; j < 2; j++) {if(i==j)


The Break Statement (Contd.)

System.out.println("InnerFor Loop");

break Outer;}

System.out.println("Outer For Loop");}

System.out.println("Loop Ended");}

}

• The preceding code output will be:Inner For Loop

Loop Ended


Summary

• You have learnt that:• Java programming language is platform-independent and object-oriented.• The PATH environment variable specifies a set of directories where executable

programs are located.• The CLASSPATH environment variable specifies the class path on a given

system.• The JVM provides a platform-independent way of executing Java code.• JRE contains JVM, class libraries, and other supporting files.• JDK contains tools to develop and run Java program.• Java programming language allows to create following application

• Stand-alone Java application• Java Applet application


Summary (Contd.)

• The a set of rules are associated with declaring classes, import statements,and package statements in a source file.

• Identifiers are the names used to identify various Java items, such as avariable, class, method, interface, and package.

• Java provides containers called variables to store data within a program.• A literal is constant value.• An array is a collection of data storage location that can holds only same type

of data.• An expression is a syntactic construction that has a value.• Operators are special symbols that perform specific operations on one, two,

or three operands, and then return a result.


Summary (Contd.)

• Operators with higher precedence are evaluated before operators withrelatively lower precedence.

• Type casting is the process of converting an entity of one data type intoanother data type.

• Statements contain the instructions to execute by the complier.• The conditional construct control statements allow a program to execute a

certain piece of code based on a decision.• The loop construct control statements allow to repeat a block of code

multiple times, while the given condition is true.• The enhanced for loop construct is designed to cycle through a collection of

objects, such as an array, in strictly sequential fashion, from start to finish.• The continue and break statements are used to stop either the current

iteration or the entire loop.


Technology

Java Day-1