LambdaExpressionInjavaforlearning fucntion

Lambda Expression in Java
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Agenda
• Lambda Expression in Java
• Use of Lambda Expression in Java
• How to write Lambda Expression in Java
• Rules for Lambda Expression in Java
• Functional Interface
• Functional Interface implementation
• Functional interface with Lambda expression
• Lambda Expression program in Java
• Lambda Vs Interface
• lambda value Capture
• Create Thread using lambda expression
• Method reference in lambda expression
• Constructor reference in lambda expression
• Exception handling in lambda expression

Lambda Expressions in Java

Lambda Expressions in Java
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• Lambda expressions are block of code without a name
• Lambda expression Implementation code can be provided when it is called
• It is a representation of anonymous class
• It can be referred as method without a name

Use of Lambda Expressions in
Java

Use of Lambda Expressions in Java
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• Advantage to use it is less coding
• The code to be used exactly once can be wrapped as lambda expression
• Encourages functional Programming

How to write Lambda
Expressions in Java

How to write Lambda Expressions in Java
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Syntax:-
1. ( one_parameter ) -> { lambda expression };
2. ( first_parameter , second_parameter ) -> { lambda expression };
3. ( ) -> {lambda expression };

Functional Interface

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• The interface having single abstract method are called functional interface
• These methods can have n number of static default methods
• Example:- Runnable, Predicate etc.

implementation

Functional Interface implementation
Predicate Interface
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public interface Predicate<T>
{
boolean test(T t);
}
public class Example implements Predicate
{
@Override
public boolean test(Object o)
{
return o == null;
}
}

Functional interface with Lambda
Expressions

Functional interface with Lambda Expressions
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• Lambda expression can be used for method implementation of one abstract method defined in
Functional Interface.
• Return type of lambda function should be same as interface type
public class Example {
public static void main(String a1[])
{
Predicate<String> p1 = x -> {
if(x == "Hello")
return true;
else
return false;
};
System.out.println(p1.test("Hello"));
}
} Proprietary content. ©Great Learning. All Rights Reserved. Unauthorized use or distribution prohibited

Rules for Lambda Expressions in
Java

Rules for Lambda Expressions in Java
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• The variable type should be of Interface type, where Interface has one method
• The lambda expression should have same number of parameters and same return type as that of
the method in that Interface

Lambda Expressions Program in
Java

Lambda Vs Interface

Lambda Vs Interface
• Lambda is used for implementing the methods of those interfaces who has only one abstract method.
• Lambda cannot be used for interface with more than one abstract methods
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Lambda Value Capture

Lambda Value Capture
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• The returned value from lambda expression can be stored in a variable of type “Interface” i.e.
object of type interface
• The variables declared in the scope of lambda expression can be accessed in lambda expression

Create Thread using Lambda
Expressions

Method reference in Lambda
Expression

Method reference in Lambda Expression
Static method reference
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Method reference in Lambda Expression
Instance method reference
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Constructor reference in Lambda
Expression

Constructor reference in Lambda Expression
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Interface StringMessage{
getString(String st);
}
Class StringExample{
StringExample(String s1){
System.out.println(“ Great “ +s1)}
}
public class Example{
public static void main(String args[]){
StringMessage m1 = StringExample :: new;
m1.getString(“Learning platform”);
}
}
Constructor reference

Exception handling in Lambda
Expression

Exception handling in Lambda Expression
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• Exception handling using try-catch for Lambda expression losses the authenticity of lambda
expressions
• A wrapper method can be created that can be used for handling the exception and then pass the
lambda expression as a parameter to this wrapper method
• This wrapper method can also be made generic

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public static void main(String[] args)
{
Predicate<Integer> p1 = x -> {
try{ if(x%2==0){return true;}
else { return false;}
}catch(Exception e){
System.out.println(e);}
};
System.out.println(p1.test(4)));
}
}

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static Predicate<Integer> WrapperP(Predicate<Integer> p1)
{
return x -> {
try{ if(x%2==0){return true;}
else { return false;}
};
public static void main(String[] args){
WrapperP((x) -> System.out.println(p1.test(4)));
}
} Proprietary content. ©Great Learning. All Rights Reserved. Unauthorized use or distribution prohibited

Summary
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We discussed
• Lambda Expression in Java
• It’s Use and How to write Lambda Expression in Java
• Functional Interface and its implementation with Lambda expression
• Lambda Expression program in Java
• Difference between Lambda and Interface
• lambda value Capture
• Creating a Thread using lambda expression
• Method and Constructor reference in lambda expression
• Exception handling in lambda expression

Thank You

LambdaExpressionInjavaforlearning fucntion

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