JAVA-method reference::

Interface Composition Update

method reference::

Method references supported by lambda expressions

Common reference methods:
referencing class methods,
referencing instance methods of objects,
referencing instance objects of classes,
referencing constructors

reference class method

Format: class name::static method
Example: Integer::parseInt
Integer class method: public static int parseInt(String s) converts this s into Int type data;
when a Lambda expression is replaced by a reference method, its formal parameters All passed to static methods as arguments

code example

public class yinyongdemo {
    
    
    public static void main(String[] args) {
    
    
        yin(s -> Integer.parseInt(s));
        yin(Integer::parseInt);//引用方法替代lambda表达式
    }
    private static void yin(yinyong y){
    
    
        int co = y.cover("788");
        System.out.println(co);
    }
}

define interface

public interface yinyong {
    
    
    int cover(String s);
}

Instance method of reference object

Format: Object::Member Method
Example: "HelloWorld"::toUpperCase
Code Example:
Main Program

public class zhuandaxiedemo {
    
    
    public static void main(String[] args) {
    
    
   //Lambda方法
    c1(s ->System.out.println(s.toUpperCase()) );
    //引用方法
        zhuanhuan zh = new zhuanhuan();
        c1(zh::a1 );
    }
    private static void c1 (zhuandaxie z){
    
    
        z.b1("jjjddd");
    }
}

Interface b1:

public interface zhuandaxie {
    
    
    void b1(String s);
}

Reference class a1:

public class zhuanhuan {
    
    
    public void a1(String a){
    
    
        String result = a.toUpperCase();
        System.out.println(result);
    }
}

Instance method of reference class

Format: class name: member method
Example: String::substring
Method in the String class: Public String substring(Int beginIndex, Int endIndex)
starts from beginIndex and ends at endIndex, intercepts the string, returns a substring, and the length of the substring is beginIndex-endIndex

reference constructor

Format: class name::new