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Variable and Datatype in Java

1. Variable

2. Types of Variable

3. Data Types in Java

In this page, we will learn about the variable and java data types. Variable is a name of

memory location. There are three types of variables local, instance and static. There are

two types of datatypes in java, primitive and non!primitive.

Variable

Variable is name of reserved area allocated in memory.

1. intdata"#$%&&'ere data is variable

Types of Variable

There are three types of variables in java

local variable
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instance variable

static variable

Local Variable

( variable that is declared inside the method is called local variable.

Instance Variable

( variable that is declared inside the class but outside the method is called instance

variable . It is not declared as static.

Static variable

( variable that is declared as static is called static variable. It cannot be local.

)e will have detailed learning of these variables in ne*t chapters.

Example to understand the types of variables

1. class(+

2. intdata"#$%&&instance variable

3. staticintm"1$$%&&static variable. voidmethod-+

#. intn"/$%&&local variable

0. . &&end of class

Data Types in Java


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In java, there are two types of data types

primitive data types

non!primitive data types

Data Type Default Value Default s

boolean false 1 bit

char 4u$$$$ 2 byte

byte $ 1 byte

short $ 2 byte

int $ byte

long $5 6 byte

float $.$f byte


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double $.$d 6 byte

Why char uses 2 byte in java and what is \u0000 ?

because java uses unicode system rather than (78II code system. 4u$$$$ is the lowest

range of unicode system.To get detail about 9nicode see below.

JVM (Java Virtual Machine)

1.Java Virtual Machine

2.Internal Architecture of JVM

:V; -:ava Virtual ;achine is an abstract machine. It is a specification that provides runtime

environment in which java bytecode can be e*ecuted.

:V;s are available for many hardware and software platforms -i.e.:V; is plateform

dependent.

What is JVM?

It is

1. A specificationwhere woruntime

?nvironment.

3. Runtime Instance)henever you write java command on the command prompt to

run the java class, and instance of :V; is created.

What it does?

The :V; performs following operation

5oads code
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Verifies code

?*ecutes code

@rovides runtime environment

:V; provides definitions for the

;emory area

8lass file format

>egister set

Aarbage!collected heap

Batal error reporting etc.

Internal Architecture of JVM

5ets understand the internal architecture of :V;. It contains classloader, memory area,

e*ecution engine etc.


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1) Classloader:

8lassloader is a subsystem of :V; that is used to load class files.

2) Class(Method) Area:

8lass-;ethod (rea stores per!class structures such as the runtime constant pool, field and

method data, the code for methods.

3) Heap:

It is the runtime data area in which objects are allocated.


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4) Stack:

:ava 7tac< stores frames.It holds local variables and partial results, and plays a part in

method invocation and return.

?ach thread has a private :V; stac


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=efore 9nicode, there were many language standards

ASCII-(merican 7tandard 8ode for Information Interchange for the 9nited

7tates.

IS !!"#-1for )estern ?uropean 5anguage.

$I-!for >ussian.

%&1!'3' and &I%-"for chinese, and so on.

Tis caused to pro*lems:

1. ( particular code value corresponds to different letters in the various languagestandards.

2. The encodings for languages with large character sets have variable length.7ome

common characters are encoded as single bytes, other reDuire two or more byte.

To solve these problems, a new language standard was developed i.e. 9nicode 7ystem.

In unicode, character holds 2 byte, so java also uses 2 byte for characters.

loest value:4u$$$$

i+est value:4uBBBB

Constructor in ,avais a special type of methodthat is used to initialiEe the object.

:ava constructor is invoked at the time of object creation. It constructs the values i.e.

provides data for the object that is why it is


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There are two types of constructors

1. Fefault constructor -no!arg constructor

2. @arameteriEed constructor

Java Default Constructor( constructor that have no parameter is


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Q) What is the purpose of default constructor?

Fefault constructor provides the default values to the object li


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Java parameterized constructor

( constructor that have parameters is


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Example of Constructor Overloading

1. class7tudent#+2. intid%

3. 7tring name%

. intage%#. 7tudent#-inti,7tring n+0. id " i%

. name " n%6.

/. 7tudent#-inti,7tring n,inta+1$. id " i%

11. name " n%12. age"a%

13. 1. voiddisplay-+7ystem.out.println-idNJ JNnameNJ JNage%

1#.

10. pu*licstaticvoidmain-7tring argsKL+

1. 7tudent# s1 " ne7tudent#-111,JOaranJ%16. 7tudent# s2 " ne7tudent#-222,J(ryanJ,2#%

1/. s1.display-%2$. s2.display-%

21. 22.

Test it o

Mutput

111 Karan 0

222 Aryan 25

Difference between constructor and method in javaThere are many differences between constructors and methods. They are given below.

Java Constructor Java Method

8onstructor is used to initialiEe the state of an object. ;ethod is used to

object.

8onstructor must not have return type. ;ethod must hav

8onstructor is invo


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The java compiler provides a default constructor if you dont have any

constructor.

;ethod is not pro

case.

8onstructor name must be same as the class name. ;ethod name ma

class name.

Java Copy ConstructorThere is no copy constructor in java. =ut, we can copy the values of one object to

another li


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Mutput

111 Karan

111 Karan

Copying values without constructor)e can copy the values of one object into another by assigning the objects values to

another object. In this case, there is no need to create the constructor.

1. class7tudent+2. intid%

3. 7tring name%. 7tudent-inti,7tring n+

#. id " i%0. name " n%

. 6. 7tudent-+

/. voiddisplay-+7ystem.out.println-idNJ JNname%1$.

11. pu*licstaticvoidmain-7tring argsKL+12. 7tudent s1 " ne7tudent-111,JOaranJ%

13. 7tudent s2 " ne7tudent-%1. s2.id"s1.id%

1#. s2.name"s1.name%10. s1.display-%

1. s2.display-%16.

1/. Test it o

Mutput

111 Karan

111 Karan

Q) Does constructor return any value?

Ans:yes, that is current class instance -Pou cannot use return type yet it returns a value.

Can constructor perform other tasks instead of initialization?
http://www.javatpoint.com/opr/test.jsp?filename=Student7http://www.javatpoint.com/opr/test.jsp?filename=Student7


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Pes, li


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7uppose there are #$$ students in my college, now all instance data members will get

memory each time when object is created.(ll student have its uniDue rollno and name so

instance data member is good.'ere, college refers to the common property of all objects.If

we ma


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Program of counter without static variableIn this e*ample, we have created an instance variable named count which is incremented in

the constructor. 7ince instance variable gets the memory at the time of object creation,

each object will have the copy of the instance variable, if it is incremented, it wont reflect to

other objects. 7o each objects will have the value 1 in the count variable.

1. class8ounter+

2. intcount"$%&&will get memory when instance is created3.

. 8ounter-+

#. countNN%0. 7ystem.out.println-count%

. 6.

/. pu*licstaticvoidmain-7tring argsKL+

1$.11. 8ounter c1"ne8ounter-%

12. 8ounter c2"ne8ounter-%13. 8ounter c3"ne8ounter-%


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1.1#.

10. Test it o

Output:1

1

1

Program of counter by static variable

(s we have mentioned above, static variable will get the memory only once, if any object

changes the value of the static variable, it will retain its value.

1. class8ounter2+

2. staticintcount"$%&&will get memory only once and retain its value3.. 8ounter2-+

#. countNN%0. 7ystem.out.println-count%

. 6.

/. pu*licstaticvoidmain-7tring argsKL+1$.

11. 8ounter2 c1"ne8ounter2-%12. 8ounter2 c2"ne8ounter2-%

13. 8ounter2 c3"ne8ounter2-%1.

1#.

10. Test it o

Output:1

2

3

2) Java static methodIf you apply static


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Example of static method

1. &&@rogram of changing the common property of all objects-static field.

2.3. class7tudent/+

. introllno%#. 7tring name%

0. static7tring college " JIT7J%.

6. staticvoidchange-+/. college " J==FITJ%

1$. 11.

12. 7tudent/-intr, 7tring n+13. rollno " r%

1. name " n%

1#. 10.

1. voiddisplay -+7ystem.out.println-rollnoNJ JNnameNJ JNcollege%16.

1/. pu*licstaticvoidmain-7tring argsKL+

2$. 7tudent/.change-%21.

22. 7tudent/ s1 " ne7tudent/ -111,JOaranJ%23. 7tudent/ s2 " ne7tudent/ -222,J(ryanJ%

2. 7tudent/ s3 " ne7tudent/ -333,J7onooJ%2#.

20. s1.display-%2. s2.display-%

26. s3.display-%2/.

3$. Test it o

Output:111 Karan BBDIT

222 Aryan BBDIT

333 Sonoo BBDIT

Another example of static method that performs normal

calculation

1. &&@rogram to get cube of a given number by static method

2.3. class8alculate+

. staticintcube-int*+#. return*Q*Q*%

0. .
http://www.javatpoint.com/opr/test.jsp?filename=Student9http://www.javatpoint.com/opr/test.jsp?filename=Student9


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6. pu*licstaticvoidmain-7tring argsKL+/. intresult"8alculate.cube-#%

1$. 7ystem.out.println-result%11.

12. Test it o

Output:125

Restrictions for static method

There are two main restrictions for the static method. They are

1. The static method can not use non static data member or call non!static method

directly.

2. this and super cannot be used in static conte*t.

1. class(+2. inta"$%&&non static3.

. pu*licstaticvoidmain-7tring argsKL+

#. 7ystem.out.println-a%0.

. Test it o

Output:Copile Tie !rror

Q) why java main method is static?

(ns because object is not reDuired to call static method if it were non!static method,

jvm create object first then call main- method that will lead the problem of e*tra

memory allocation.

3) Java static block

o Is used to initialiEe the static data member.

o It is e*ecuted before main method at the time of classloading.

Example of static block

1. class(2+2. static+7ystem.out.println-Jstatic bloc< is invo


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3. pu*licstaticvoidmain-7tring argsKL+. 7ystem.out.println-J'ello mainJ%

#. 0.

Test it o

Output:static "lock is in#oked

$ello ain

Q) Can we execute a program without main() method?

(ns Pes, one of the way is static bloc< but in previous version of :FO not in :FO 1..

1. class(3+

2. static+3. 7ystem.out.println-Jstatic bloc< is invo


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. this can be passed as an argument in the method call.

#. this can be passed as argument in the constructor call.

0. this


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1. Test it o

Output:0 null

0 null

In the above e*ample, parameter -formal arguments and instance variables are same

that is why we are using this


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If local variables-formal arguments and instance variables are different, there is no need

to use this


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2) this() can be used to invoked current class constructor.

The this- constructor call can be used to invo


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0. 7tudent1-intid,7tring name+. tis.id " id%

6. tis.name " name%/.

1$. 7tudent1-intid,7tring name,7tring city+11. tis-id,name%&&now no need to initialiEe id and name

12. tis.city"city%13. 1. voiddisplay-+7ystem.out.println-idNJ JNnameNJ JNcity%

1#.

10. pu*licstaticvoidmain-7tring argsKL+1. 7tudent1 e1 " ne7tudent1-111,J


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Pou may invo


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3. 7ystem.out.println-Jmethod is invo


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Test it o

Output:10

6) The this keyword can be used to return current class instance.

)e can return the this


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. (# obj"ne(#-%6. 7ystem.out.println-obj%&&prints the reference IF

/.1$. obj.m-%

11. 12.

Test it o

Output:A522"3ea5

A522"3ea5

next prev

Inheritance in Java

1. Inheritance

2. ypes of Inheritance

3. !hy multiple inheritance is not possible in "ava in case of class#

Ineritance in ,avais a mechanism in which one object acDuires all the properties and

behaviors of parent object.

The idea behind inheritance in java is that you can create new classes that are built upon

e*isting classes. )hen you inherit from an e*isting class, you can reuse methods and

fields of parent class, and you can add new methods and fields also.

Inheritance represents the IS-A relationsip, also eusability.

Syntax of Java Inheritance
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1. class7ubclass!name e/tends7uperclass!name

2. +3. &&methods and fields

.

The e/tends 0eordindicates that you are maelationship between two classes is ro+rammer IS-A .mploee.It means

that @rogrammer is a type of ?mployee.

1. class?mployee+

2. floatsalary"$$$$%3.

. class@rogrammer e/tends?mployee+#. intbonus"1$$$$%

0. pu*licstaticvoidmain-7tring argsKL+. @rogrammer p"ne@rogrammer-%


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6. 7ystem.out.println-J@rogrammer salary isJNp.salary%

/. 7ystem.out.println-J=onus of @rogrammer isJNp.bonus%1$.

11.

Test it o

ro-raer salary is:400000

Bonus o& pro-raer is:10000

In the above e*ample, @rogrammer object can access the field of own class as well as of

?mployee class i.e. code reusability.

Types of inheritance in javaMn the basis of class, there can be three types of inheritance in java single, multilevel

and hierarchical.

In java programming, multiple and hybrid inheritance is supported through interface

only. )e will learn about interfaces later.
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Note: ultiple inheritance is not supported in java throu!h class.

)hen a class e*tends multiple classes i.e.


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3.

. class=+#. voidmsg-+7ystem.out.println-J)elcomeJ%

0. . class8 e/tends(,=+&&suppose if it were

6.

/. @ublic 7tatic voidmain-7tring argsKL+1$. 8 obj"ne8-%

11. obj.msg-%&&Row which msg- method would be invo


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1) super is used to refer immediate parent class

instance variable.

Problem without super keyword

1. classVehicle+2. intspeed"#$%

3. . class=i


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Test it o

Output:50

2) super is used to invoke parent class constructor.The super


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the first statement of the constructor.

Another example of super keyword where super() is provided by the

compiler implicitly.

1. classVehicle+2. Vehicle-+7ystem.out.println-JVehicle is createdJ%

3. .

#. class=i


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7elcoe

In the above e*ample 7tudent and @erson both classes have message- method if we

call message- method from 7tudent class, it will call the message- method of 7tudent

class not of @erson class because priority is given to local.

In case there is no method in subclass as parent, there is no need to use super. In the

e*ample given below message- method is invo


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voidanotherEat*+ ) super-eat*+0 11

publicclassest)

publicstaticvoidmain*,tring23 args+ ) Animala 4 newAnimal*+0 a-eat*+0 %ogd 4 new%og*+0 d-eat*+0 d-anotherEat*+0 11

The output is going to be

animal / eatdog / eatanimal / eat

The third line is printing "animal:eat" because we are calling super-eat*+. Ifwe called this-eat*+, it would have printed as "dog:eat".

Aggregation in Java

If a class have an entity reference, it is


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Why use Aggregation?

Bor 8ode >eusability.

,imple Example of Aggregation

In this e*ample, we have created the reference of Mperation class in the 8ircle class.

1. classMperation+2. intsDuare-intn+

3. returnnQn%.

#. 0.

. class8ircle+

6. Mperation op%&&aggregation/. dou*lepi"3.1%

1$.11. dou*learea-intradius+

12. op"neMperation-%

13. int rsDuare"op.sDuare-radius%&&code reusability -i.e. delegates the method call.1. returnpiQrsDuare%

1#. 10.

1.16.

1/. pu*licstaticvoidmain-7tring argsKL+

2$. 8ircle c"ne8ircle-%21. dou*leresult"c.area-#%22. 7ystem.out.println-result%

23. 2.

Test it o

Output:(85
http://www.javatpoint.com/opr/test.jsp?filename=Circlehttp://www.javatpoint.com/opr/test.jsp?filename=Circle


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When use Aggregation?

8ode reuse is also best achieved by aggregation when there is no is!a relationship.

Inheritance should be used only if the relationship is!a is maintained throughout the

lifetime of the objects involved% otherwise, aggregation is the best choice.

$nderstanding meaningful example of Aggregation

In this e*ample, ?mployee has an object of (ddress, address object contains its own

informations such as city, state, country etc. In such case relationship is ?mployee '(7!(

address.

Address.java

1. pu*licclass(ddress +2. 7tring city,state,country%

3.. pu*lic(ddress-7tring city, 7tring state, 7tring country +

#. tis.city " city%0. tis.state " state%

. tis.country " country%

6. /.

1$.

Emp.java

1. pu*licclass?mp +

2. intid%3. 7tring name%

. (ddress address%#.

0. pu*lic?mp-intid, 7tring name,(ddress address +. tis.id " id%

6. tis.name " name%

/. tis.address"address%1$. 11.

12. voiddisplay-+

13. 7ystem.out.println-idNJ JNname%1. 7ystem.out.println-address.cityNJ JNaddress.stateNJ JNaddress.country%

1#. 10.

1. pu*licstaticvoidmain-7tringKL args +


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16. (ddress address1"ne(ddress-JgEbJ,J9@J,JindiaJ%1/. (ddress address2"ne(ddress-JgnoJ,J9@J,JindiaJ%

2$.21. ?mp e"ne?mp-111,JvarunJ,address1%

22. ?mp e2"ne?mp-112,JarunJ,address2%23.

2. e.display-%2#. e2.display-%20.

2.

26.

Test it o

Output:111 #arun

-9" india

112 arun

-no india

prev

Object Cloning in Java

The o*,ect clonin+is a way to create e*act copy

of an object. Bor this purpose, clone- method of Mbject class is used to clone an object.

The,avalan+Clonea*le interfacemust be implemented by the class whose object clone

we want to create. If we dont implement 8loneable interface, clone- method

generates CloneotSupported./ception.
http://www.javatpoint.com/opr/test.jsp?filename=Emphttp://www.javatpoint.com/encapsulationhttp://www.javatpoint.com/opr/test.jsp?filename=Emphttp://www.javatpoint.com/encapsulation


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The clone() metodis defined in the Mbject class. 7ynta* of the clone- method is as

follows

1. protectedMbject clone- tros8loneRot7upported?*ception

Why use clone() method ?

The clone() metodsaves the e*tra processing tas< for creating the e*act copy of an

object. If we perform it by using the new


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Output:101 ait

101 ait

download the example of ob"ect cloning

(s you can see in the above e*ample, both reference variables have the same value. Thus,

the clone- copies the values of an object to another. 7o we dont need to write e*plicit code

to copy the value of an object to another.

If we create another object by new


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The final


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2) Java final methodIf you ma


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1. class=iFHR9;=?>%#. ...

0.

Que) Can we initialize blank final variable?

Pes, but only in constructor. Bor e*ample

1. class=i


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Method Overriding in Java

1.Understanding problem without method overriding

2.Can we override the static method

3.method overloading vs method overriding

If subclass -child class has the same method as declared in the parent class, it is


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0. pu*licstaticvoidmain-7tring argsKL+. =i


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1. class=anateMfInterest-+return$%3. .

#. class7=I e/tends=anateMfInterest-+return6%

. 6.

/. classI8I8I e/tends=anateMfInterest-+return%

11. 12. class(SI7 e/tends=anateMfInterest-+return/%1.

1#.

10. classTest2+1. pu*licstaticvoidmain-7tring argsKL+

16. 7=I s"ne7=I-%

1/. I8I8I i"neI8I8I-%2$. (SI7 a"ne(SI7-%

21. 7ystem.out.println-J7=I >ate of Interest JNs.get>ateMfInterest-%22. 7ystem.out.println-JI8I8I >ate of Interest JNi.get>ateMfInterest-%

23. 7ystem.out.println-J(SI7 >ate of Interest JNa.get>ateMfInterest-%2.

2#.

Test it o

Output:

SBI ;ate o& Interest: 8

ICICI ;ate o& Interest: (

A


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Ro, static method cannot be overridden. It can be proved by runtime polymorphism, so we

will learn it later.

Why we cannot override static method?

because static method is bound with class whereas instance method is bound with object.

7tatic belongs to class area and instance belongs to heap area.

Can we override java main method?

Ro, because main is a static method.

Difference between method overloading and

method overriding in java

There are many differences between method overloading and method overriding in java. (

list of differences between method overloading and method overriding are given below

No. Method Overloading Method Overrid

1

;ethod overloading is used to increase the readabilityof the

program.

;ethod overriding i

specific implementa

already provided by

2

;ethod overloading is performed within class. ;ethod overriding o

have I7!( -inherita

3

In case of method overloading,parameter must be different. In case of method o

must be same.

;ethod overloading is the e*ample of compile time

polymorphism.

;ethod overriding i

polymorphism.


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#

In java, method overloading cant be performed by changing

return type of the method only. Return type can be same or

differentin method overloading. =ut you must have to change

the parameter.

Return type must b

method overriding.

Java Method Overloading example1. classMverloading?*ample+2. staticintadd-inta,intb+returnaNb%

3. staticintadd-inta,intb,intc+returnaNbNc%.

Java Method Overriding example1. class(nimal+

2. voideat-+7ystem.out.println-Jeating...J%3. . classFog e/tends(nimal+

#. voideat-+7ystem.out.println-Jeating bread...J%0.

Encapsulation in Java

.ncapsulation in ,avais aprocess of wrapping code and data together into a single unit,

for e*ample capsule i.e. mi*ed of several medicines.

)e can create a fully encapsulated class in java by ma


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=y providing only setter or getter method, you can ma


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olmorpism in ,avais a concept by which we can perform a single action by different

ways. @olymorphism is derived from 2 gree< words poly and morphs. The word JpolyJ

means many and JmorphsJ means forms. 7o polymorphism means many forms.

There are two types of polymorphism in java compile time polymorphism and runtimepolymorphism. )e can perform polymorphism in java by method overloading and method

overriding.

If you overload static method in java, it is the e*ample of compile time polymorphism. 'ere,

we will focus on runtime polymorphism in java.

Runtime Polymorphism in JavaRuntime polmorpismor 4namic 5etod 4ispatcis a process in which a call to an

overridden method is resolved at runtime rather than compile!time.

In this process, an overridden method is called through the reference variable of a

superclass. The determination of the method to be called is based on the object being

referred to by the reference variable.

5ets first understand the upcasting before >untime @olymorphism.

Upcasting

)hen reference variable of @arent class refers to the object of 8hild class, it is


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Example of 8ava 9untime Polymorphism

In this e*ample, we are creating two classes =i


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Rote It is also given in method overriding but there was no upcasting.

1. class=anateMfInterest-+return$%

3. .

#. class7=I e/tends=anateMfInterest-+return6%.

6./. classI8I8I e/tends=anateMfInterest-+return%

11. 12. class(SI7 e/tends=anateMfInterest-+return/%

1. 1#.

10. classTest3+1. pu*licstaticvoidmain-7tring argsKL+

16. =an< b1"ne7=I-%1/. =an< b2"neI8I8I-%

2$. =an< b3"ne(SI7-%21. 7ystem.out.println-J7=I >ate of Interest JNb1.get>ateMfInterest-%

22. 7ystem.out.println-JI8I8I >ate of Interest JNb2.get>ateMfInterest-%23. 7ystem.out.println-J(SI7 >ate of Interest JNb3.get>ateMfInterest-%

2. 2#.

Test it o

Output:

SBI ;ate o& Interest: 8

ICICI ;ate o& Interest: (
http://www.javatpoint.com/opr/test.jsp?filename=Test3http://www.javatpoint.com/opr/test.jsp?filename=Test3


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Auntime @olymorphism with multilevel inheritance.

1. class(nimal+2. voideat-+7ystem.out.println-JeatingJ%

3. .

#. classFog e/tends(nimal+

0. voideat-+7ystem.out.println-Jeating fruitsJ%. 6.

/. class=abyFog e/tendsFog+1$. voideat-+7ystem.out.println-Jdrin


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1#. a2"neFog-%10. a3"ne=abyFog-%

1.16. a1.eat-%

1/. a2.eat-%2$. a3.eat-%

21. 22.

Test it o

Output: eatin-

eatin- &ruits

drinkin- *ilk

Try for Output

1. class(nimal+2. voideat-+7ystem.out.println-Janimal is eating...J%3.

.#. classFog e/tends(nimal+

0. voideat-+7ystem.out.println-Jdog is eating...J%.

6./. class=abyFog1 e/tendsFog+

1$. pu*licstaticvoidmain-7tring argsKL+11. (nimal a"ne=abyFog1-%

12. a.eat-%

13. Test it o

Output: Do- is eatin-

7ince, =abyFog is not overriding the eat- method, so eat- method of Fog class is invo


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2. new #eyword

Java Strin+provides a lot of concepts that can be performed on a string such as compare,

concat, eDuals, split, length, replace, compareTo, intern, substring etc.

In java, string is basically an object that represents seDuence of char values.

(n array of characters wor


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1) String Literal

:ava 7tring literal is created by using double Duotes. Bor ?*ample

1. 7tring s"JwelcomeJ%

?ach time you create a string literal, the :V; chec


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that it will find the string with the value J)elcomeJ in the pool, it will not create new object

but will return the reference to the same instance.

Note: String objects are stored in a special memory area known as string constant pool.

Why java uses concept of string literal?

To ma


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e?aple

Java String class methods

The java.lang.7tring class provides many useful methods to perform operations on seDuence

of char values.

No. Method Description

1 char char(t-int inde* returns char value

2 int length- returns string lengt

3 static 7tring format-7tring format, Mbject... args returns formatted s

static 7tring format-5ocale l, 7tring format, Mbject... args returns formatted s

# 7tring substring-int beginInde* returns substring fo

0 7tring substring-int beginInde*, int endInde* returns substring fo

end inde*

boolean contains-8har7eDuence s returns true or fals

seDuence of char va

6 static 7tring join-8har7eDuence delimiter, 8har7eDuence...

elements

returns a joined str

/ static 7tring join-8har7eDuence delimiter, IterableGC e*tends

8har7eDuence elements

returns a joined str

1$ boolean eDuals-Mbject another chec


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1# 7tring trim- returns trimmed st

trailing spaces

10 7tring split-7tring rege* returns splitted stri

1 7tring split-7tring rege*, int limit returns splitted stri

limit

16 7tring intern- returns interned str

1/ int inde*Mf-int ch returns specified ch

2$ int inde*Mf-int ch, int fromInde* returns specified ch

with given inde*

21 int inde*Mf-7tring substring returns specified su

22 int inde*Mf-7tring substring, int fromInde* returns specified su

with given inde*

23 7tring to5ower8ase- returns string in low

2 7tring to5ower8ase-5ocale l returns string in low

locale.

2# 7tring to9pper8ase- returns string in up

20 7tring to9pper8ase-5oca

next prev

Immutable String in Java

In java, strin+ o*,ects are immuta*le. Immutable simply means unmodifiable or

unchangeable.

Mnce string object is created its data or state cant be changed but a new string object is

created.

5ets try to understand the immutability concept by the e*ample given below
http://www.javatpoint.com/java-string-trimhttp://www.javatpoint.com/java-string-splithttp://www.javatpoint.com/java-string-splithttp://www.javatpoint.com/java-string-internhttp://www.javatpoint.com/java-string-indexofhttp://www.javatpoint.com/java-string-indexofhttp://www.javatpoint.com/java-string-indexofhttp://www.javatpoint.com/java-string-indexofhttp://www.javatpoint.com/java-string-tolowercasehttp://www.javatpoint.com/java-string-tolowercasehttp://www.javatpoint.com/java-string-touppercasehttp://www.javatpoint.com/java-string-touppercasehttp://www.javatpoint.com/string-comparison-in-javahttp://www.javatpoint.com/string-handling-in-javahttp://www.javatpoint.com/java-string-trimhttp://www.javatpoint.com/java-string-splithttp://www.javatpoint.com/java-string-splithttp://www.javatpoint.com/java-string-internhttp://www.javatpoint.com/java-string-indexofhttp://www.javatpoint.com/java-string-indexofhttp://www.javatpoint.com/java-string-indexofhttp://www.javatpoint.com/java-string-indexofhttp://www.javatpoint.com/java-string-tolowercasehttp://www.javatpoint.com/java-string-tolowercasehttp://www.javatpoint.com/java-string-touppercasehttp://www.javatpoint.com/java-string-touppercasehttp://www.javatpoint.com/string-comparison-in-javahttp://www.javatpoint.com/string-handling-in-java


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1. classTestimmutablestring+

2. pu*licstaticvoidmain-7tring argsKL+3. 7tring s"J7achinJ%

. s.concat-J Tendul


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still refers to J7achinJ not to J7achin Tendul


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)e can compare string in java on the basis of content and reference.

It is used in autentication-by eDuals- method, sortin+-by compareTo-

method, reference matcin+-by "" operator etc.

There are three ways to compare string in java

1. =y eDuals- method

2. =y " " operator

3. =y compareTo- method

1) String compare by equals() methodThe 7tring eDuals- method compares the original content of the string. It compares values

of string for eDuality. 7tring class provides two methods

o pu*lic *oolean e6uals(*,ect anoter)compares this string to the specified

object.

o pu*lic *oolean e6ualsI+noreCase(Strin+ anoter)compares this 7tring to

another string, ignoring case.

1. classTeststringcomparison1+

2. pu*licstaticvoidmain-7tring argsKL+3. 7tring s1"J7achinJ%

. 7tring s2"J7achinJ%#. 7tring s3"ne7tring-J7achinJ%

0. 7tring s"J7auravJ%. 7ystem.out.println-s1.eDuals-s2%&&true

6. 7ystem.out.println-s1.eDuals-s3%&&true


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/. 7ystem.out.println-s1.eDuals-s%&&false1$.

11. Test it o

Output:true

true

&alse



. 7tring s2"J7(8'IRJ%#.

0. 7ystem.out.println-s1.eDuals-s2%&&false. 7ystem.out.println-s1.eDualsIgnore8ase-s3%&&true

6.

/. Test it o

Output:&alse

true

8lic< me for more about eDuals- method

2) String compare by == operatorThe " " operator compares references not values.



. 7tring s2"J7achinJ%#. 7tring s3"ne7tring-J7achinJ%

0. 7ystem.out.println-s1""s2%&&true -because both refer to same instance. 7ystem.out.println-s1""s3%&&false-because s3 refers to instance created in nonpo

ol6.

/. Test it o

Output:true

&alse
http://www.javatpoint.com/opr/test.jsp?filename=Teststringcomparison1http://www.javatpoint.com/opr/test.jsp?filename=Teststringcomparison2http://www.javatpoint.com/java-string-equalshttp://www.javatpoint.com/opr/test.jsp?filename=Teststringcomparison3http://www.javatpoint.com/opr/test.jsp?filename=Teststringcomparison1http://www.javatpoint.com/opr/test.jsp?filename=Teststringcomparison2http://www.javatpoint.com/java-string-equalshttp://www.javatpoint.com/opr/test.jsp?filename=Teststringcomparison3


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3) String compare by compareTo() methodThe 7tring compareTo- method compares values le*icographically and returns an integer

value that describes if first string is less than, eDual to or greater than second string.

7uppose s1 and s2 are two string variables. If

o s1 77 s2$

o s1 8 s2 positive value

o s1 9 s2 negative value

1. classTeststringcomparison+2. pu*licstaticvoidmain-7tring argsKL+

3. 7tring s1"J7achinJ%

. 7tring s2"J7achinJ%#. 7tring s3"J>atanJ%

0. 7ystem.out.println-s1.compareTo-s2%&&$

. 7ystem.out.println-s1.compareTo-s3%&&1-because s1s36. 7ystem.out.println-s3.compareTo-s1%&&!1-because s3 G s1

/. 1$.

Test it o

Output:0

1

=1

String Concatenation in Java

In java, string concatenation forms a new string that isthe combination of multiple strings.

There are two ways to concat string in java

1. =y N -string concatenation operator

2. =y concat- method

1) String Concatenation by + (string concatenation)

operator:ava string concatenation operator -N is used to add strings. Bor ?*ample
http://www.javatpoint.com/opr/test.jsp?filename=Teststringcomparison4http://www.javatpoint.com/opr/test.jsp?filename=Teststringcomparison4


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1. classTest7tring8oncatenation1+2. pu*licstaticvoidmain-7tring argsKL+

3. 7tring s"J7achinJNJ Tendul


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Sac+in Tendulkar

Documents

java intrvw conecpts details.docx