The document explains lambda expressions in Java, describing them as anonymous methods that implement functional interfaces. It outlines the syntax, components, and rules for using lambda expressions, as well as providing examples for implementation. Additionally, it contrasts traditional thread implementations with those using lambda expressions for streamlined code.

1. Lambda Expression
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2. Lambda Expression
• It is an anonymous (that is, unnamed) method
• A lambda expression results in a form of anonymous class.
• This method is not executed on its own. Instead, it is used to implement a
method defined by a functional interface.
• Lambda expressions are also commonly referred to as closures
Dr.M.S.Bhuvaneswari, SCORE,VIT

3. Lambda Expression Fundamentals
• The lambda expression introduces a new syntax element and operator into the
Java language
• lambda operator or the arrow operator
• Lambda operator divides the lambda expression into two parts.
• The left side specifies any parameters required by the lambda expression.
• On the right side is the lambda body, which specifies the actions of the lambda
expression
• Syntax:
(param1,param2) -> body
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4. Lambda Expression Fundamentals
• lambda expression consist of three components:
▪ Argument-list: It can be empty or non-empty as well.
▪ Arrow-token: It is used to link arguments-list and body of expression.
▪ Body: It contains expressions and statements for lambda expression.
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5. Lambda Expression
• No Parameter Syntax
() -> {
//Body of no parameter lambda
}
• One Parameter Syntax
(param1) -> {
//Body of no parameter lambda
}
Dr.M.S.Bhuvaneswari, SCORE,VIT

6. Lambda Expression
Multiple parameter Syntax
(param1, param2) -> {
//Body of no parameter lambda
}
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7. Functional Interface
• A functional interface is an interface that contains one and only one abstract method.
Example: Runnable is a functional interface because it defines only one method
run( )
• It typically represents a single action.
• A functional interface defines the target type of a lambda expression.
• When a lambda expression occurs in a target type context, an instance of a class is
automatically created that implements the functional interface, with the lambda
expression defining the behavior of the abstract method declared by the functional
interface
• A functional interface is sometimes referred to as a SAM type, where SAM stands for
Single Abstract Method.
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8. Lambda Expression Fundamentals
• Java defines two types of lambda bodies.
▪ single expression
▪ block of code
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Normal Method
=============
int findSum()
{
return 20;
}
Lambda Expression
================
() -> 20

9. Lambda Expression
• In order for a lambda expression to be used in a target type context, the type of
the abstract method and the type of the lambda expression must be compatible
• Rules
▪ The type and number of the lambda expression’s parameters must be
compatible with the method’s parameters;
▪ The return types must be compatible; and
▪ Any exceptions thrown by the lambda expression must be acceptable to the
method
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10. Lambda Expression Example1
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interface FuncIntf {
public int getValue();
}
class ClsIntf implements FuncIntf
{
public int getValue()
{
return 20;
}
}
class MyClass
{
public static void main(String[] args)
{
FuncIntf intfRef = new ClsInft();
System.out.println("Value is:"+intfRef.getValue());
}
}

11. Lambda Expression Example1
Dr.M.S.Bhuvaneswari, SCORE,VIT
interface FuncIntf {
int getValue();
}
class MyClass
{
public static void main(String[] args)
{
FuncIntf intfRef = new ClsInft();
System.out.println("Value is:"+intfRef.getValue());
}
}

12. Lambda Expression Example1
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interface FuncIntf {
int getValue();
}
class MyClass
{
public static void main(String[] args)
{
FuncIntf intfRef = ;
System.out.println("Value is:"+intfRef.getValue());
}
}

13. Lambda Expression Example1
Dr.M.S.Bhuvaneswari, SCORE,VIT
interface FuncIntf {
int getValue();
}
class MyClass
{
public static void main(String[] args)
{
FuncIntf intfRef = () -> 20;
System.out.println("Value is:"+intfRef.getValue());
}
}
Lambda Expression () -> 20
================
• Implements the method getValue() in FuncIntf
• Returns an instance of the class

14. Lambda Expression with parameters - Example2
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interface FuncIntf
{
int findSum(int a,int b);
}
class MyClass
{
public static void main(String[] args)
{
FuncIntf intfRef = (x,y)-> {int c=x+y;return c;};
System.out.println("Value is:"+intfRef.findSum(6,8));
}
}

15. Lambda Expression with parameters type- Example3
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interface FuncIntf
{
int findSum(int a,int b);
}
class MyClass
{
public static void main(String[] args)
{
FuncIntf intfRef = (int x, int y)-> {int c=x+y;return c;};
System.out.println("Value is:"+intfRef.findSum(6,8));
}
}

16. Lambda Expression with parameters type- Example4
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interface FuncIntf
{
int findSum(int a,int b);
}
class MyClass
{
public static void main(String[] args)
{
FuncIntf intfRef = (int x, int y)-> {int c=x+y;return c;}; //with return(with multiple statements)
System.out.println("Value is:"+intfRef.findSum(6,8));
FuncIntf intfRef1 = (int x,int y)-> (x+y); //without return(with only one statement)
System.out.println("Value is:"+intfRef1.findSum(6,8));
}
}

17. Thread Implementation without Lambda
class MyThread implements Runnable{
public void run()
{
try {
for(int i = 5; i > 0; i--) {
System.out.println("Child Thread: " + i);
Thread.sleep(500);
}
}
catch (InterruptedException e) {
System.out.println("Child interrupted.");
}
System.out.println("Exiting child thread.");
}
}
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18. Thread Implementation without Lambda
Runnable rintf=new MyThread()
Thread th1=new Thread(rintf)
th1.start()
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19. Thread Implementation using Lambda
Thread th1=new Thread(() -> {
try {
for(int i = 5; i > 0; i--) {
System.out.println("Child Thread: " + i);
Thread.sleep(500);
}
}
catch (InterruptedException e) {
System.out.println("Child interrupted.");
}
System.out.println("Exiting child thread.");
});
th1.start();
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20. References
• https://www.javatpoint.com/java-lambda-expressions