JavaClassPresentation

James Gosling
Welcome
To
Programming in JAVA

By
Mr. A. Julias Ceasor
Bosco Institute of Information Technology

After this unit will be over, you will be the
Know-how of the followings:

Java Basics:
OOP and Java - Objects and Classes – Encapsulation -
Inheritance - Polymorphism - Java Language - The Primaries -
Character Set - Tokens - Constants - Variables - Operators
and Expressions - Library Methods - Strings - I/O Streams -
Formatting the Output values - Control Statements – If -
Switch - While - Do-While-for.

Java Fundamentals & Basics for
Programming
What is Java?
Java is a programming language expressly designed for use in
the distributed environment of the Internet. It was designed to
have the "look and feel" of the C++ language, but it is simpler to
use than C++ and enforces an object-oriented programming
model.

Key Concept of Java:
• Java Technology is:
- Simple, Secure, Robust, Complete Object Oriented and Platform
Independent High level Language.
- It is portable and Multi-thread technology gives High
performance.
• It is based on concept called JVM.
- Act as a translator between the language and the underlying
Software and Hardware.

What is Object Oriented Programming?
• This is a technique used to develop programs revolving around
the real world entities.
• In OOPs programming model, programs are developed around
data rather than actions and logics.
• In OOPs, every real life object has properties and behavior.
• It contains properties (variables of some type) and behavior
(methods).
• OOPs provides a better flexibility and compatibility for developing
large applications.

What is object?
• Object is a real world entity.
• the Real world Objects are: Building, Objects
Car, Fruit,… and etc.

Attributes:
• Four Wheels
• Engine
• Seats
An Object • Steering
• Speed
• Disk Break
• Etc.

Functionalities
(Methods):
+Wheels for Rolling
Car + Engine for Moving
+Seats for Sitting
+Break for Control
+Etc.

Programming Object:
- It is combination of Data and Methods.

An Object

Attributes of
an object Method Method
(-) Functionalitie
s of an
Object
Data
(+)

Method Method

Object = Data + Methods

Pillars of OOPL:

OOPL

PolymorphismDynamic Binding
Inheritance Encapsulation

Why the Java?
• C, C++ and other programming languages are not flexible for
complex problems.
• Other languages are Structured and Object Oriented
Programming language. Not Fully OOPL.
• Others are not Platform Independent.

Evolution of Java
• In 1990, the group of engineers developed a software for consumer
electronics at Sun micro System of USA.
• This group is headed by James Gosling.
• In 1991, it is proved that it satisfy the concepts of OOPL like C++
and called as 'Oak' by James Gosling.
• In 1992, the Green Project is started.
• In 1993, the team developed small applet program for World Wide
Web.
• In 1994, the team came up with browser called HotJava.
• In 1995, the 'Oak' renamed as 'Java'

Why is it named 'Oak'?
When the 'Ever green' team was Developed Software for
consumer Electronics, such as Set-Top-Boxes, and Other hand
held devices, the Head of the team James Gosling saw a Oak tree
in front of his office.
The Oak tree is a ever green tree and never its leaves get dry. Due
to this reason, the software named as 'Oak'.

Features of Java:
• Java is:
 simple
 easy to design
 easy to write
 and therefore easy to compile
 debug
 and learn than any other programming languages.

• Java is object-oriented, that is used to build modular programs and
reusable code in other application.

• Java is platform-independent and flexible in nature.

• The most significant feature of Java is to run a program easily from
one computer system to another.

Continued…..

• Java works on distributed environment.

• Java is secure. The Java language, compiler, interpreter and
runtime environment are securable .

• Java is robust. Robust means reliability.

• Java emphasis on checking for possible errors.

• Java supports multithreaded. Multithreaded is the path of
execution for a program to perform several tasks simultaneously
within a program.

Java Platform:
• Platform is cross-combination of hardware or software environment
in which a program runs.

Environment
Operates and for Java
Controls H/W Development

Java Platform

Software (OS) Platform

Hardware Platform

Java Platform:
• Java Platform has Two Components.
1. Java Virtual Machine (JVM)
2. Java Application Programming Interface (API)

JVM API

JVM:
The Java Virtual Machine is the root for the Java platform and is
integrated into various hardware-based platforms.
API:
The API is a vast collection of various software components that
provide you many useful functionality to the application.
It is grouped into logical collection of related classes and interfaces;
these logical collection are known as packages.

How it Works:

•All source code is written in text files (Notepad Editor) save with
the .java extension
• The source files are compiled into .class files by the java
compiler. A .class file contains byte codes
• The java launcher tool runs your application with an instance of
the Java Virtual Machine.

Execution of Program as Platform Independent

A simple Java Program:
HelloWorld.java

import java.io.*;

class HelloWorld
{
public static void main(String args[])
{
System.out.println("HelloWorld");
}
}
Output:
HelloWorld

Procedure for developing java application
1. Write a java source code as a text file (can create in notepad) using
any of the text editor.
• Save the file with .java extension in your directory.
• The filename should be the class name of the program.
• Open the command prompt to run the application
• Compile the code with command javac filename.java
• Run the class file with the command java filename
• The output will be displayed on your console.

Two ways of using Java

Java
Source
Code

Applet Type Application
Java Compiler Type

Java
Enabled Java
Web Interpreter
Browser

Output Output

Java Technology:
On full implementation of the Java platform gives you the following
features:

JDK Tools: The JDK tools provide compiling, Interpreter, running,
monitoring, debugging, and documenting your applications. The main tools
used are the Javac compiler, the java launcher, and the javadoc
documentation tool.
Application Programming Interface (API): The API provides the core
functionality of the Java programming language.

Deployment Technologies: The JDK software provides two type of
deployment technology such as the Java Web Start software and Java Plug-
In software for deploying your applications to end users.

Graphical User Interface Toolkits: The Swing and Java 2D toolkits provide
us the feature of Graphical User Interfaces (GUIs).

Integrated Libraries: Integrated with various libraries such as the Java IDL
API, JDBC API, Java Naming and Directory Interface TM ("J.N.D.I.") API,
Java RMI, and Java Remote Method Invocation over Internet.

Structure of Java Program

A set of comment lines giving the name
Documentation Section
of the program, author and other details.
/**…….*/ or // or /*…..*/
Package Statements
Declare the package names and inform
the compiler the class defined below
belongs to Statements e.g.: package
Import this packages.
student;the interpreter to load the test
Instruct
class contained in Student package. E.g.
Interface Statements
import student.test;
Includes a group of methods
declarations.
Class Definitions

Can have multiple class declarations.
Main Method Class
{
Main method Definition
Creates objects of various classes and
}
establishes communication between

Java Virtual Machine:
• All language compiler translate source code into machine code for specific
computer.
• Java compiler produces an intermediate code known as bytecode for a
machine that does not exist.
• This machine is called Java Virtual Machine (JVM)
• It is simulated computer with in a computer does all major functions.
• the bytecode is called as virtual machine code.
• this is not machine specific.
• Machine specific code is generated by Java Interpreter by acting as
intermediary between the virtual machine and real machine.
• Illustrated below.

Process of Compilation:

Java Virtual
Program Machine
Source code Bytecode

Java Compiler

Process of Converting bytecode into
machine code

Machine Code

Bytecode

Virtual
Machine
Java Real
Interpreter Machine

Classes and Objects:
Class:
A class is a programming language construct that is used as a
blueprint to create objects. This blueprint describes the state and
behavior that the created objects all share.

E.g.: Bicycles

• There may be thousands of other
bicycles in existence, all of the same
make and model.
• Each bicycle was built from the
same set of blueprints and therefore
contains the same components.
• In object-oriented terms, we say that
your bicycle is an instance of the
class of objects known as bicycles.
• A class is the blueprint from which
individual objects are created.

The following Bicycle class is one possible implementation of a bicycle:

class Bicycle {

int cadence = 0;
int speed = 0;
int gear = 1;

void changeCadence(int newValue)
{
cadence = newValue;
}

void changeGear(int newValue)
{
gear = newValue;
}
void speedUp(int increment)
{
speed = speed + increment;
}
void applyBrakes(int decrement)
{
speed = speed - decrement;
}

Here's a BicycleDemo class that creates two
separate Bicycle objects and invokes their methods:

class BicycleDemo { • The fields cadence,
public static void main(String[] args) { speed, and gear
represent the object's
// Create two different Bicycle objects state, and the methods
Bicycle bike1 = new Bicycle(); (changeCadence,
Bicycle bike2 = new Bicycle(); changeGear, speedUp
etc.) define its
// Invoke methods on those objects interaction with the
bike1.changeCadence(50); outside world.
bike1.speedUp(10);
bike1.changeGear(2);
bike1.printStates(); • It is just the blueprint for
bicycles that might be
bike2.changeCadence(40); used in an application
bike2.speedUp(10);
bike2.changeGear(3);
bike2.printStates();
}
}

The output of this test prints the ending pedal
cadence, speed, and gear for the two bicycles:
cadence:50 speed:10 gear:2 cadence:40 speed:20

Object:
Object is the basic entity of object oriented programming language.
Class itself does nothing but the real functionality is achieved through
their objects. Object is an instance of the class. It takes the properties
(variables) and uses the behavior (methods) defined in the class.

E.g.: Bicycle

• Real-world objects share two characteristics: They all have state
and behavior.
• Dogs have state (name, color, breed, hungry) and behavior (barking,
fetching, wagging tail).
• Bicycles also have state (current gear, current pedal cadence,
current speed) and behavior (changing gear, changing pedal
cadence, applying brakes).
• Identifying the state and behavior for real-world objects is a great
way to begin thinking in terms of object-oriented programming.
• Ask yourself: "What possible states can this object be in?" and
"What possible behavior can this object perform?". Make sure to
write down your observations.

• An object stores its state in fields (variables in some
programming languages)
• And exposes its behavior through methods (functions in some
programming languages).

A Software Object

Data Encapsulation:
Hiding internal state and requiring all interaction to be performed
through an object's methods is known as data encapsulation — a
fundamental principle of object-oriented programming.

Bundling code into individual software objects provides a
number of benefits, including:

Modularity:
The source code for an object can be written and maintained
independently of the source code for other objects.
Information-hiding:
By interacting only with an object's methods, the details of its
internal implementation remain hidden from the outside world.
Code re-use:
If an object already exists (perhaps written by another software
developer), you can use that object in your program.
Pluggability and debugging ease:
If a particular object turns out to be problematic, you can simply
remove it from your application and plug in a different object as
its replacement.

Main Pillars of OOP:
Encapsulation:
• Abstraction: Hiding the information (Complexities) to the end users.
E.g.: User Driving a Car.
• Encapsulation is the process of binding together the methods and
data variables as a single entity.
• It keeps both the data and functionality code safe from the
outside world.
• It hides the data within the class and makes it available only
through the methods.
• Java provides different accessibility scopes (public, protected,
private ,default) to hide the data from outside.

Example:
Here we create a class "Check" which has a variable "amount" to store the
current amount. To manipulate this variable we create a methods and to
set the value of amount we create setAmount() method and to get the value
of amount we create getAmount() method .

class Check{
private int amount=0;
public int getAmount(){
return amount;
}
public void setAmount(int amt){
amount=amt;
}
}
public class Mainclass{
public static void main(String[] args){
int amt=0;
Check obj= new Check();
obj.setAmount(200);
amt=obj.getAmount();
System.out.println("Your current amount is :"+amt);
}
}

Here the data variable "amount" and methods setAmount() and
getAmount() are enclosed together with in a single entity called the
"Check" class.

Inheritance:
• Inheritance allows a class (subclass) to acquire the properties and
behavior of another class (superclass).
• In java, a class can inherit only one class (superclass) at a time
but a class can have any number of subclasses.
• It helps to reuse, customize and enhance the existing code.
• So it helps to write a code accurately and reduce the
development time. Java uses extends keyword to extend a class.

Class A

Class B inherits
Fun 1
the property
of class A
Extends

Class B

Fun 2

class A{
public void fun1(int x){
System.out.println("Int in A is :" + x);
}
}
class B extends A{
public void fun2(int x,int y){
fun1(6); // prints "int in A"
System.out.println("Int in B is :" + x+" and "+y);
}
}
public class inherit{
B obj= new B();
obj.fun2(2,6);
}
}

In the above example, class B extends class A and so
acquires properties and behavior of class A. So we can call
method of A in class B.

Polymorphism :
• Polymorphism allows one interface to be used for a set of actions i.e.
one name may refer to different functionality.
• Polymorphism allows a object to accept different requests of a
client (it then properly interprets the request like choosing
appropriate method) and responds according to the current state
of the runtime system, all without bothering the user.

There are two types of polymorphism :
1.Compile-time polymorphism (Method Overloading)
2.Runtime Polymorphism (Method Overriding)

Method Overloading:
• In compiletime Polymorphism, method to be invoked is determined at
the compile time.
• Compile time polymorphism is supported through the method
overloading concept in java.
• Method overloading means having multiple methods with same name
but with different signature (number, type and order of parameters).

Method Overloading (Compile-time polymorphism)

class A{
System.out.println("The value of class A is : " + x);
}
public void fun1(int x,int y){
System.out.println("The value of class B is : " + x + " and " +
y);
}
}
public class polyone{
A obj=new A();
// Here compiler decides that fun1(int)
is to be called and "int" will be printed.
obj.fun1(2);
// Here compiler decides that fun1(int,int)is to be called and "int
and int" will be printed.
obj.fun1(2,3);
}
}

Method Overriding:
• In Run-time polymorphism, the method to be invoked is
determined at the run time.
• The example of run time polymorphism is method overriding.
When a subclass contains a method with the same name and
signature as in the super class then it is called as method
overriding.

Method Overriding (Run-time Polymorphism)

class A{
System.out.println("int in Class A is : "+ x);
}
}

class B extends A{
System.out.println("int in Class B is : "+ x);
}
}

public class polytwo{
A obj;

obj= new A(); // line 1
obj.fun1(2); // line 2 (prints "int in Class A is : 2")

obj=new B(); // line 3
obj.fun1(5); // line 4 (prints ""int in Class B is : 5")
}

Character Set in Java:
• The smallest units of java languages are Characters used to
write Java Tokens.
• These characters are defined by Unicode Character set.
• The Unicode is a 16-bit character coding system.
• It supports more than 34,000 characters in worldwide.
• ASCII characters are subset of UNICODE Character set.

lower-case <= a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z
upper-case <= A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|
W|X|Y|Z
alphabetic <= lower-case | upper-case
numeric <= 0|1|2|3|4|5|6|7|8|9
alphanumeric <= alphabetic | numeric
special <= !|%|^|&|*|(|)|-|+|=|{|}|||~|[|]||;|'|:|"|<|>|?|,|.|/|#|@|`|_
graphic <= alphanumeric | special

Java Tokens:
•Smallest individual units in a program are known as tokens.
•The compiler recognizes them for building up expressions and
statements.
•Java language includes Five types of tokens. They are:
•Reserved Keywords
•Identifiers
•Literals
•Operators
•Separators

Keywords:
•Keyword are an essential part of a language definition.
•Java has 50 keywords listed below.
•Keywords have specific meaning in Java.
•We cannot use them as names for variables, classes, methods and so
on.
• All keywords are to be written in lower-case letters.
•It is good practice avoiding usage of key words as identifiers.
•keywords are case-sensitive.

List of Keywords in Java
abstract continue goto package switch
assert default if private this
boolean do implements protected throw
break double import public throws
byte Else Instanceof Return Transient
Case Extends Int Short Try
Catch Final Interface Static Void
Char Finally Long Strictfp Volatile
Class Float Native Super While
Const For New Synchronized enum

Identifiers:
•Identifiers are programmer-designed tokens. They are used for
naming classes, methods, variables, objects, labels, packages
and interfaces in a program.
•Rules for Identifiers:
1. They can have alphabets, digits, underscore and dollar
sign characters.
• They must not begin with digit.
• Uppercase and lowercase letters are distinct.
• They can be of any length.

Literals:
Literals in Java are a sequence of characters (digits, letters, and
other characters) that represent constant values to be stored in
variables.

Java specifies Five major types of literals. They are:

• Integer Literals E.g.: 123
• Floating-point Literals E.g.: 123.45
• Character Literals E.g.: 'X' or 'x'
• String Literals E.g.: "Hello"
• Boolean Literals E.g.: true or false

Operators:
An operator is a symbol that takes one or more arguments and
operates on them to produce a result.
Separators:
Separators are symbols used to indicate where groups of code
are divided and arranged.

separators

Note that the first three separators are tokens that
separate/punctuate other tokens. The last six separators (3-pairs of
2 each) are also known as delimiters.
For example the Java code Math.max(count,limit); contains nine
; , . ( ) { } [ ]
tokens.
• An identifier (math), followed by
• A separator (a period), followed by
• Another identifier (max), followed by
• A separator (the left parenthesis delimiter), followed by
• An identfier (count), followed by
• A separator (a comma), followed by
• Another identifier(limit), followed by
• A separator (the right parenthesis delimiter), followed by
• A separator (a semicolon)

Java Statements

Expression
Statements
Labeled
Statements
Control Synchronize
Statements
Guarding
Statements
St.

Selection Iteration Jump
Statements Statements Statements

break return
if switch

continue
If-
else

while do for

Constants:
Definition:
Constants in Java refer to fixed values that do not change
during the execution of a program.

Java Constants

Java Constants Java Constants

Integer Real Character String
Constants Constants Constants Constants
Decimal : 123 E.g.:
Fractional : 0.0065,-0.75 E.g.:
Octal : 037 "Hello" "1223"
Exponential : 1.5e+5 '5' 'X' ';'
Hexadecimal: 0X9F

Integer Constants:
An integer constant refers to a sequence of digits.
Real Constant:
A constant which has fractional part is called Real constant.
Character Constant:
A single character constant (or simply character constant) contains a
single character enclosed within a pair of single quote marks.
String Constant:
A string constant is a sequence of characters enclosed between
double quotes.
Backslash Character Constants:
'b', 'f', 'n', 'r', 't', '"', '"', ''

Variables:
A variable is an identifier that denotes a storage location used to store
a data value. Unlike constants that remain unchanged during the
execution of a program.
Rules for variable names:
1. They must not begin with a digit.
• Uppercase and lowercase are distinct.
• It shou8ld not be a keyword.
• White space is not allowed.
• Variable names can be of any length.

Declaration of variables:
Variables are the names of storage locations. After designing suitable
variable names, we must declare them to the compiler.
type variable1, variable2, …………, variableN;
Declaration does :
1. Tell the compiler what the variable name is.
• Specify what type of data the variable will hold.
• Decides the scope of variable (depends on the place it is declared).

Scope of Variables:
The area of the program where the variable is accessible is called its scope.
It is classified into three kinds:
• Instance variable
• Class variable
• Local variable
Instance:
Instance variable is declared inside the class. It is created when the objects
are instantiated and therefore they are associated with the objects. They take
different values for different object.
Class:
It is also declared inside the class and it is global variable to a class and
belong to the entire set of objects that creates. Only one memory location is
created for each class.
Local:
Variables declared and used inside methods are called local variables. And it
also can be declared inside the block of codes that defined between { and }.

Data Types in Java:
• Data types specify the size and type of values that can be stored.
• Variety of data types available allow the programmer to select the
type appropriate to the needs of the application.

DATA TYPES IN JAVA

Primitive Non-Primitive
(Intrinsic) (Derived)

Numeric Non-Numeric Classes Arrays

IntegerFloating-
Character Boolean
Interface
Point

Integer Type:
• Can hold whole numbers such as 123, -234.
• It has Four types of Integer Types:
o Byte
o Short
o Int
o Long

Floating Point Types:
• Can hold numbers containing fractional parts such as 57.78 and
-45.78.
• It has two types of values:
o Single Precision
o Double precision

Character Type:
• To store character constant in memory the data type Char is
used.
• It assumes a size of 2 bytes and holds a single character.
Boolean type:
this type of data type is used to hold the values of Boolean such as
‘true’ or ‘false’.
Symbolic Constants:
Storing of some Constant value (which is needed frequently in the
program) to a symbol is called Symbolic Constant.
final type symbolic-name = value;
E.g.: final int STRENGTH = 100;
Type Casting:
The process of Converting one data type to another is called casting.
type variable1 = (type) variable2;

Operators:
Operators are used in programs to manipulate data and variables.
The list of Operators:
1. Arithmetic operators
• Relational operators
• Logical operators
• Assignment operators
• Increment and decrement operators
• Conditional operators
• Bitwise operators
• Special operators

Arithmetic Operators

Operator Meaning
<
+ Is less than
Addition or unary plus
<= Is less than or equal to
- Subtraction or unary minus
> Is greater than
* Multiplication
>= Is greater than or equal to
/
== Division
Is equal to
Relational Operators
!=
% Moduloequal to
Is not division

Logical Operators

Operator Meaning
++
=
&& Incrementing value
Store value
Logical AND
--
|| Decrementing value
Logical OR
! Assignment Operator
Logical NOT

Increment and decrement Operators

Conditional Operator

Exp1 ? Exp2 : exp3

Bitwise Operators

Operator Meaning
& Bitwise AND
| Bitwise OR
^ Bitwise exclusive OR
~ One's complement
<< Shift left
>> Shift right
>>> Special Operators zero fill
Shift right with

Instanceof Operator:
E.g.: person instanceof student
Dot Operator:
E.g.: person.age

postfix [] . () expr++ expr–
unary ++expr –expr +expr -expr ! ~
creation/caste new (type)expr
multiplicative */%
additive +-
shift >> >>>
relational < <= > >= instanceof
equality == !=
bitwise AND &
bitwise exclusive OR ^
bitwise inclusive OR |
logical AND &&
logical OR ||
ternary ?:
assignment = “op=”

Operator Precedence

Control Statements:
There are two types of control statements. They are:
1. Decision making and Branching Statements
• Decision making and Looping statements

Decision making and Branching:
•when a program breaks the sequential flow and jumps to another part
of the code, it is called branching.
•When the branching is based on a particular condition, it is known as
conditional branching.
•If branching takes place without any decision, it is known as
unconditional branching.
They are:
1. If statement
• Switch statement
• Conditional operator statement

If Statement:
The four forms of If statement:
1. Simple if
• If….else
• Nested if…else
• Else if ladder

Simple if: Entry
General form:
if (test expression) true
{ Test
?
statement-block;
} Statements block
False
statement-X;

Statements X

Next statements

If…Else statement:
Entry
General form:
if (test expression)
False Test true
{
True-block statement; ?
}
Statements block
False Statements block
else
{
False-block statement; Statements X
}
statement-X;
Next statements

Conditional Operator:

General form:

Conditional expression ? Expression-1 : Expression-2

Nested If…Else statement:
General form:
{
if (test expression) Entry
{
True-block statement; False Test true
} ?
else
{ Statements block
False Test true
False-block statement; False
?
}
} Statements Statements
else
{
False-block statement;
} Statements X
statement-X;

Else…If Ladder:
General form:
Entry
else if (test expression)
False Test true
Statement-1;
else if (test expression) ?
Statement-2;
Statements block
False
else False Test true
Default St; ?
Statement-X; Statements

Test
False
?

Statements true
Default

Statements X

Switch Statement:
General form:
Switch (expression)
{
case value-1:
blockt-1;
break;
case value-1:
blockt-1;
break;
default:
default-block;
break;
}
Statement-X;

Loop Controls:
There are three types of looping statements:
1. While construct
• Do construct
• For construct
A looping process, in general,
would include the following four steps:
1. Setting and initialization of a counter
• Execution of the statements in the loop
• Test for a specified condition for execution of the loop
• Incrementing the counter

Loop control structures:

Entry Entry

False
Test
?
Body of the loop

true true

Body of the loop
Test
?
False

Entry control
Exit control

The While Statement: The for Statement:
Entry Controlled Loop. Another entry Controlled Loop.
General Form: General Form:
Initialization; for (initialization; test-condition;
While (test-condition) increment)
{ {
Body of the loop; Body of the loop;
} }

The do Statement: Nesting of for Loops:
Exit Controlled Loop. General Form:
General Form: for (initialization; test-condition;
Initialization; increment)
do {
{ for (initialization; test-condition;
Body of the loop; increment)
} {
While (test-condition); Body of the loop;
}
}

Jump in Loops: Skipping a Part of a Loop:
During the loop operations, it may
Java permits a jump from one
be necessary to skip a part of the
statement to the end or beginning
body of the loop under certain
of a loop as well as out of loop.
conditions.
Jumping Out of Loop:
the continue statement causes the
General Form:
loop to be continued with the next
Initialization;
iteration after skipping.
While (test-condition)
General Form:
{ ………….
Initialization;
………….
While (test-condition)
if (condition)
{ ………….
break;
………….
Body of the loop;
} Exit from loop if (condition)
continue;
……………..
Body of the loop; Skip the
……………..
} iteration
……………..
……………..

Labeled Loops:
General Form:
Outer: While (test-condition)
{ ………….
………….
if (condition)
Body of the loop;
Transferring
continue Outer;
} Control
……………..
……………..

Java Library Methods:
Strings:
In Java string is a sequence of characters. Java implements strings as
objects of type String.
String Constructors:

String(char chars[])
String(char chars[], int startindex, int numChars)
String(String strObj)
Strin(byte asciiChars[])
String(byte asciiChars[], int startIndex, int numChars)
Where: startIndex • specify the subrange begins and numChars •
specify the number of characters to use.
Declaration: E.g.: String S = new String();

Methods in String Description
int length() Return the length of the string
String toString() Converts data into string representation
Char charAt(int where) Returns a character at index specified
Void getChars(int sourceStart, Extract the specified characters from one string
int sourceEnd, char target[], int to another
targetStart)
char[] toCharArray() Returns an array of characters
boolean equals(Object str) Returns boolean value
Boolean startsWith(String str) Returns boolean value
Boolean endsWith(String str) Returns boolean value

int compareTo(String str) If value is: < 0 • Invoking String is less than str
> 0 • Invoking String is greater than str
== 0 • Invoking String equal to str
String substring(int Separate the substring from main string
startIndex,int endIndex)
String concat(String str) Concatenation of two strings
String replace(char original, Replace the string
char replace)
String trim() Remove the white space in a string.

Methods in String Description
Static String value(double Converts data into human readable format
num)
String toLowerCase() Converts letters to lower case
String to UpperCase() Converts letters to Uppercase
Char charAt(int where) Return a character
Void setCharAt(int where, Set the character at its position
char ch)
StringBuffer delete(int start,Delete the content at specified position.
int end) and StringBuffer
deleteCharAt(int where)
StringBuffer replace(int Replace the string at specified positions
start, int end, String str)
'+' is a Concatenation It just join the strings or data
operator of Strings or any
Data types.

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