Types of Method References

There are 3 use cases in Method Reference

• Pass as an argument
• Pass an argument to a static method
• Pass aargument as a target
• Two parameters as an argument

  //valueOf is a static method in String class which converts any data type to String
  import java.util.Arrays;
  import java.util.List;
  
  public class Sample {
      public static void main(String[] args) {
  
  	List<Integer> numbers= Arrays.asList(1,2,3,4,5,6,7,8,9,10);
  	    System.out.println("Pass as an argumernt");
  	    //here println is refernece to an Instance method
  	    numbers.forEach(System.out::println);
  
  
  	System.out.println("Pass as an argumernt to a static method ");
  	numbers.stream()
  		// .map(e->String.valueOf(e))
  		.map(String::valueOf)           //Here valueOf (which is a static method) is a reference to a static method
  		.forEach(System.out::println);
  
  
  
  	System.out.println("Pass as a target");
  	numbers.stream()
  		.map(e-> e.toString())
  		.forEach(System.out::println);
  
  	numbers.stream()
  		.map(e->String.valueOf(e))
  		.map(String::toString)
  		.forEach(System.out::println);
  	}
  
  
  
  	System.out.println("Two parameters as an argument");
  	System.out.println(
         numbers.stream()
  	       .reduce(0,(total,e)-> Integer.sum(total,e)));
  //method references are only useful when the order is the same (total,e) != (e,total) becz other methods might not allow it
  	System.out.println(
        numbers.stream().reduce(0,Integer::sum));
  }}
  
  

Edit this page on GitHub