Java Lambda Tutorial For Beginners | Lambda Expression In Java | Java Tutorial | Simplilearn

2. Agenda What is Lambda? Functional Interface Lambda v/s Method Lambda as an Object Variable Captures Method References Best Practices

3. Lambda Tutorial What is Lambda?

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5. What is Lambda? Lambda is similar to a Code Segment or a Method but does not have a name. It can be implemented inside a method just like any regular method in Java

6. Lambda Tutorial Need for Lambda?

7. Need of Lambda? Lambda converts the code segment into an argument A method that can be created without instantiating a class Lambda can be treated as an Object

8. Lambda Tutorial Syntax of Lambda

9. Syntax of Lambda parameter -> expression (parameter 1, parameter 2) -> expression (parameter 1, parameter 2) { //Code Segment }

10. Lambda Tutorial Functional Interface

11. Functional Interface A Functional interface contains only one unimplemented abstract method. It can contain default and static methods which do have an implementation, in addition to the single unimplemented method

12. Lambda Tutorial Example

13. Lambda Tutorial Lambda v/s Method

14. Lambda v/s Method Method Lambda Name is necessary It doesn’t need name May or may not include parameters May or may not include parameters It has a return-type It does not have a return-type Code Body is just another code segment of the program Includes Body as the main code segment

15. Lambda Tutorial Lambda as an Object

16. Lambda as an Object Compare compare = (x,y) -> return x<y; greater result = Compare.compare(10, 100); Java Lambda Expression is essentially an object. You can assign a Lambda Expression to a variable and pass it around, like you do with a normal object

17. Lambda Tutorial Variable Captures

18. Variable Captures Java lambdas can capture the following types of variables: Local variables Instance variables Static variables A Java lambda expression can access variables declared outside the lambda function body under certain circumstances

19. Variable Captures JavaLambdajavalambda = (chars) -> { return new String(chars); }; A Java lambda can capture the value of a local variable declared outside the lambda body

20. Variable Captures String str = “alphabet"; JavaLambdajavalambda = (chars) -> { return str + ":" + new String(chars); };

21. Variable Captures A lambda expression can capture an instance variable in the object that creates the lambda

22. Variable Captures public class CompanyID { private String val = “Employee"; public void attach(EmpIDCreateEmpID){ EmpID.listen(e -> { System.out.println(this.val); }); } }

23. Variable Captures Java Lambda Expression can capture static variables. Static variables are reachable from everywhere in a Java program, but provided the static variable is public)

24. Variable Captures public class CompanyID { private static String val = “Employee"; public void attach(EmpIDCreateEmpID){ EmpID.listen(e -> { System.out.println(this.val); }); } }

25. Lambda Tutorial Method References

26. Method References Java lambda has three types Method References Reference to a static method Reference to an instance method Reference to a constructor Method reference is used to refer method of functional interface. It is compact and easy form of lambda expression. Each time when you are using lambda expression to just referring a method, you can replace your lambda expression with method reference

27. Lambda Tutorial Best Practices

28. Best Practices Prefer using Standard Functional Interfaces Make a habit of using  @FunctionalInterface Annotation Avoid Overuse of Default Methods in Functional Interfaces Instantiate Functional Interfaces With Lambda Expressions Avoid Overloading Methods With Functional Interfaces as Parameters