Lambda Expression For anyone that needs Java Lambda notes

Java Lambda expression concept

1. Lambda Expression
Dr.M.S.Bhuvaneswari, SCORE,VIT

2. Lambda Expression
•Itisananonymous(thatis,unnamed)method
•Alambdaexpressionresultsinaformofanonymousclass.
•Thismethodisnotexecutedonitsown.Instead,itisusedtoimplementa
methoddefinedbyafunctionalinterface.
•Lambdaexpressionsarealsocommonlyreferredtoasclosures
Dr.M.S.Bhuvaneswari, SCORE,VIT

3. Lambda Expression Fundamentals
•Thelambdaexpressionintroducesanewsyntaxelementandoperatorintothe
Javalanguage
•lambdaoperatororthearrowoperator
•Lambdaoperatordividesthelambdaexpressionintotwoparts.
•Theleftsidespecifiesanyparametersrequiredbythelambdaexpression.
•Ontherightsideisthelambdabody,whichspecifiestheactionsofthelambda
expression
•Syntax:
(param1,param2)->body
Dr.M.S.Bhuvaneswari, SCORE,VIT

4. Lambda Expression Fundamentals
•lambdaexpressionconsistofthreecomponents:
▪Argument-list:Itcanbeemptyornon-emptyaswell.
▪Arrow-token:Itisusedtolinkarguments-listandbodyofexpression.
▪Body:Itcontainsexpressionsandstatementsforlambdaexpression.
Dr.M.S.Bhuvaneswari, SCORE,VIT

5. Lambda Expression
•NoParameterSyntax
()->{
//Bodyofnoparameterlambda
}
•OneParameterSyntax
(param1)->{
//Bodyofnoparameterlambda
}
Dr.M.S.Bhuvaneswari, SCORE,VIT

6. Lambda Expression
MultipleparameterSyntax
(param1,param2)->{
//Bodyofnoparameterlambda
}
Dr.M.S.Bhuvaneswari, SCORE,VIT

7. Functional Interface
•Afunctionalinterfaceisaninterfacethatcontainsoneandonlyoneabstractmethod.
Example:Runnableisafunctionalinterfacebecauseitdefinesonlyonemethod
run()
•Ittypicallyrepresentsasingleaction.
•Afunctionalinterfacedefinesthetargettypeofalambdaexpression.
•Whenalambdaexpressionoccursinatargettypecontext,aninstanceofaclassis
automaticallycreatedthatimplementsthefunctionalinterface,withthelambda
expressiondefiningthebehavioroftheabstractmethoddeclaredbythefunctional
interface
•AfunctionalinterfaceissometimesreferredtoasaSAMtype,whereSAMstandsfor
SingleAbstractMethod.
Dr.M.S.Bhuvaneswari, SCORE,VIT

8. Lambda Expression Fundamentals
•Javadefinestwotypesoflambdabodies.
▪singleexpression
▪blockofcode
Dr.M.S.Bhuvaneswari, SCORE,VIT
NormalMethod
=============
intfindSum()
{
return20;
}
LambdaExpression
================
()->20

9. Lambda Expression
•Inorderforalambdaexpressiontobeusedinatargettypecontext,thetypeof
theabstractmethodandthetypeofthelambdaexpressionmustbecompatible
•Rules
▪Thetypeandnumberofthelambdaexpression’sparametersmustbe
compatiblewiththemethod’sparameters;
▪Thereturntypesmustbecompatible;and
▪Anyexceptionsthrownbythelambdaexpressionmustbeacceptabletothe
method
Dr.M.S.Bhuvaneswari, SCORE,VIT

10. Lambda Expression Example1
Dr.M.S.Bhuvaneswari, SCORE,VIT
interfaceFuncIntf{
publicintgetValue();
}
classClsIntfimplementsFuncIntf
{
publicintgetValue()
{
return20;
}
}
classMyClass
{
publicstaticvoidmain(String[]args)
{
FuncIntfintfRef=newClsInft();
System.out.println("Valueis:"+intfRef.getValue());
}
}

11. Lambda Expression Example1
Dr.M.S.Bhuvaneswari, SCORE,VIT
interfaceFuncIntf{
intgetValue();
}
classMyClass
{
publicstaticvoidmain(String[]args)
{
FuncIntfintfRef=newClsInft();
System.out.println("Valueis:"+intfRef.getValue());
}
}

12. Lambda Expression Example1
Dr.M.S.Bhuvaneswari, SCORE,VIT
interfaceFuncIntf{
intgetValue();
}
classMyClass
{
publicstaticvoidmain(String[]args)
{
FuncIntfintfRef=;
System.out.println("Valueis:"+intfRef.getValue());
}
}

13. Lambda Expression Example1
Dr.M.S.Bhuvaneswari, SCORE,VIT
interfaceFuncIntf{
intgetValue();
}
classMyClass
{
publicstaticvoidmain(String[]args)
{
FuncIntfintfRef=()->20;
System.out.println("Valueis:"+intfRef.getValue());
}
}
LambdaExpression()->20
================
•ImplementsthemethodgetValue()inFuncIntf
•Returnsaninstanceoftheclass

14. Lambda Expression with parameters -Example2
Dr.M.S.Bhuvaneswari, SCORE,VIT
interfaceFuncIntf
{
intfindSum(inta,intb);
}
classMyClass
{
publicstaticvoidmain(String[]args)
{
FuncIntfintfRef=(x,y)->{intc=x+y;returnc;};
System.out.println("Valueis:"+intfRef.findSum(6,8));
}
}

15. Lambda Expression with parameters type-Example3
Dr.M.S.Bhuvaneswari, SCORE,VIT
interfaceFuncIntf
{
intfindSum(inta,intb);
}
classMyClass
{
publicstaticvoidmain(String[]args)
{
FuncIntfintfRef=(intx,inty)->{intc=x+y;returnc;};
System.out.println("Valueis:"+intfRef.findSum(6,8));
}
}

16. Lambda Expression with parameters type-Example4
Dr.M.S.Bhuvaneswari, SCORE,VIT
interfaceFuncIntf
{
intfindSum(inta,intb);
}
classMyClass
{
publicstaticvoidmain(String[]args)
{
FuncIntfintfRef=(intx,inty)->{intc=x+y;returnc;}; //withreturn(withmultiplestatements)
System.out.println("Valueis:"+intfRef.findSum(6,8));
FuncIntfintfRef1=(intx,inty)->(x+y); //withoutreturn(withonlyonestatement)
System.out.println("Valueis:"+intfRef1.findSum(6,8));
}
}

17. Thread Implementation without Lambda
classMyThreadimplementsRunnable{
publicvoidrun()
{
try{
for(inti=5;i>0;i--){
System.out.println("ChildThread:"+i);
Thread.sleep(500);
}
}
catch(InterruptedExceptione){
System.out.println("Childinterrupted.");
}
System.out.println("Exitingchildthread.");
}
}
Dr.M.S.Bhuvaneswari, SCORE,VIT

18. Thread Implementation without Lambda
Runnablerintf=newMyThread()
Threadth1=newThread(rintf)
th1.start()
Dr.M.S.Bhuvaneswari, SCORE,VIT

19. Thread Implementation using Lambda
Threadth1=newThread(()->{
try{
for(inti=5;i>0;i--){
System.out.println("ChildThread:"+i);
Thread.sleep(500);
}
}
catch(InterruptedExceptione){
System.out.println("Childinterrupted.");
}
System.out.println("Exitingchildthread.");
});
th1.start();
Dr.M.S.Bhuvaneswari, SCORE,VIT

20. References
•https://www.javatpoint.com/java-lambda-expressions