Java: Method Reference

 

1. 类名::引用实例方法
   Java 类名只能引用静态方法, 类名引用实例方法是 拿第一个参数作为方法的调用者
   

   import java.util.function.BiFunction;
   import java.util.function.Function;
   
   public class addThen{
     public static void main(String[] args){
       Function<String, Integer> f1 = s -> s.length();
       System.out.println("f1.apply(\"etymology\") = " + f1.apply("etymology"));
   
       Function<String, Integer> f2 = String::length;
       System.out.println("f2.apply(\"etymology\") = " + f2.apply("etymology"));
   
       BiFunction<String, Integer, String> biFunction = String::substring;
       System.out.println("biFunction.apply(\"etymology\",3) = " + biFunction.apply("etymology", 3));
     }
   }

    

2. 类名::new
   

   import java.util.function.BiFunction;
   import java.util.function.Supplier;
   
   public class addThen{
     public static void main(String[] args){
       Supplier<Jot> supplier1 = Jot::new;
       System.out.println("supplier1 = " + supplier1.get());
   
       BiFunction<String,Integer,Jot> supplier2=Jot::new;
       System.out.println("\033[37;7m" + supplier2.apply("jot", 55) + "\033[0m");
   
     }
   }
   
   class Jot{
     String name;
     int age;
   
     @Override
     public String toString(){
       final StringBuilder sb = new StringBuilder("Jot{");
       sb.append("name='").append(name).append('\'');
       sb.append(", age=").append(age);
       sb.append('}');
       return sb.toString();
     }
   
     public Jot(){
     }
   
     public Jot(String name, int age){
       this.name = name;
       this.age = age;
     }
   }

    

3. 数组::new        String[]::new
   

   public class addThen{
     public static void main(String[] args){
       Function<Integer,String[]> f1=len->new String[len];
       String[] strings = f1.apply(5);
       System.out.println("strings = " + Arrays.toString(strings));
   
       Function<Integer,String[]>  f2=String[]::new;
       String[] strings1 = f2.apply(3);
       System.out.println("strings1 = " + Arrays.toString(strings1));
     }
   }