A Lambda Expression in Java is a feature introduced in Java 8. It helps developer to write clean , concise & flexible code, particularly when dealing with functional interfaces. It enable us to use functionality as a method argument. Lambda expressions enable you to create anonymous functions(functions without a name) which can be passed around the code as a variables.
Lambda expression is already used in many languages before like LISP, C++, C#, SCALA, RUBY etc & lately introduced in java .
The main objective of Lambda Expression is –
1: To Enable Functional Programming Language in Java.
2: To write clean , concise & flexible code.
3: To use API very easily and effectively.
4: To Enable parallel processing.
Lambda Expression is an anonymous function not having name, return type and modifier.
Lambda expression is a function which does not have any have modifier , return type & mehod name . Let us try to write and convert a normal function to equivalante lambda expression.
Convert Normal Function to Lambda Expression (without argument and no return type)
// Normal function without parameter
public void testLambda(){
System.out.println("I am Lambda");
}
// Lambda function
()-> {System.out.println("I am Lambda");}
Convert Normal Function to Lambda Expression (with argument and no return type)
// Normal Function with argument
public void testLambda( int a , int b){
System.out.println(a+b);
}
// equivalent Lambda wxpression with argument
(int a, int b)->{
System.out.println(a+b);
}
Convert Normal Function to Lambda Expression (with argument and return type)
// Normal Function with argument & return type
public int testLambda( int a , int b){
System.out.println(a+b);
}
// equivalent Lambda function with argument & return type
(int a, int b)->{
return a*b;
}
If Lambda expression has only one statement , we can ignore curly braces.
(a ,b)-> System.out.println("I am Lambda");
Sometimes compiler can guess the datatype based on the context then we can remove data type as well & if there is only one statement we remove curly brces & return keyword too. If there is only argument we can remove parenthesis as well . so the most simplified version of lambda express is-
public int nameLength( String name){
return name.length();
}
// Lambda Expression
s-> s.length();
Lets Summarize the Properties Of Lambda Expression below:
1: A lambda expression can take any number of Parameter
()-> System.out.println(“Java”); // Zero Parameter
(s)->s.length(); // One Parameter
(a+b)-> System.out.println(a+b); // Two Parameter
2: if there is only one parameter, we can ignore the parenthesis
s->s.length();
3: We can ignore the type of parameter if compiler can expect the type based on content then we can remove the type as well. This is called “Type Inference “.
(a,b)->System.out.println(a+b);
4: If lambda expression containes more than one statement then all the statements must enclose within curly braces;
()->{
Statement 1;
Statement 1;
Statement 1;
}
5: If Lambda Expression return something, we can ignore ‘return’ keyword also
s->s.length();
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