Java: FunctionalInterface

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java.util.function 定义了一些预定义FuncationInterface

Supplier:

import java.util.function.Supplier;

public class addThen{
  public static void main(String[] args){
    for(int i = 0; i < 10; i++){
      jot(() -> (int) Math.floor(Math.random() * 5 + 1));
    }
  }
  // 生成 Supplier 生成 [1,5]间随机数
  public static void jot(Supplier<Integer> supplier){
    Integer integer = supplier.get();
    System.out.println("integer = " + integer);
  }
}

Consumer:

import java.util.Locale;
import java.util.function.Consumer;

public class addThen{
  public static void main(String[] args){
    jot(s->{
      System.out.println("s = " + s);
      System.out.println("s.toUpperCase(Locale.ROOT) = " + s.toUpperCase(Locale.ROOT));
    },s->{
      System.out.println("s = " + s);
      System.out.println("s.toLowerCase(Locale.ROOT) = " + s.toLowerCase(Locale.ROOT));
    });
  }

  public static void jot(Consumer<String> c1, Consumer<String> c2){
    c1.andThen(c2).accept("etymology");
  }
}

 Function:

import java.util.function.Function;

public class addThen{
  public static void main(String[] args){
    jot(Integer::parseInt, "55");
  }
  // String -> Integer
  private static void jot(Function<String, Integer> function, String s){
    Integer integer = function.apply(s);
    System.out.println("integer = " + integer);
  }
}

import java.util.function.Function;

public class addThen{
  public static void main(String[] args){
    jot(Integer::parseInt, Integer::doubleValue, "55");
  }

  // String -> Integer -> Double
  private static void jot(Function<String, Integer> f1, Function<Integer, Double> f2, String s){
    Double aDouble = f1.andThen(f2).apply(s);
    System.out.println("aDouble = " + aDouble);
  }
}

import java.util.function.Function;

public class addThen{
  public static void main(String[] args){
    jot(Integer::parseInt, Integer::doubleValue, "55");
  }

  // String -> Integer -> Double
  // 与andThen处理顺序不同, 先调用f1, 把f1结果作为参数给f2
  private static void jot(Function<String, Integer> f1, Function<Integer, Double> f2, String s){
    Double aDouble = f2.compose(f1).apply(s);
    System.out.println("aDouble = " + aDouble);

  }
}

import java.util.function.Function;

public class addThen{
  public static void main(String[] args){
    Function<Integer, Integer> identity = Function.identity();
    Integer integer = identity.apply(5);
    System.out.println("integer = " + integer);
    Integer modulus = identity.andThen(i -> i % 3).andThen(i -> (int) Math.pow(i, 3)).apply(11);
    System.out.println("modulus = " + modulus);
  }
}

Predicate:

import java.util.function.Predicate;

public class addThen{
  public static void main(String[] args){
    jot(s -> s.contains("jot"), "jotq");
  }

  private static void jot(Predicate<String> predicate, String message){
    boolean flag = predicate.test(message);
    System.out.println("flag = " + flag);
  }
}

import java.util.function.Predicate;

public class addThen{
  public static void main(String[] args){
    jot(s->s.contains("jot"),s->s.contains("qw"),"jotqwer");
  }

  private static void jot(Predicate<String> p1,Predicate<String> p2, String message){
    boolean flag = p1.and(p2).test(message);
    System.out.println("flag = " + flag);
  }
}

import java.util.function.Predicate;

public class addThen{
  public static void main(String[] args){
    jot(s -> s.contains("jot"), s -> s.contains("qw"), "jotqwer");
  }

  private static void jot(Predicate<String> p1, Predicate<String> p2, String message){
    boolean flag = p1.and(p2).negate().test(message);
    System.out.println("flag = " + flag);
  }
}

import java.util.function.Predicate;

public class addThen{
  public static void main(String[] args){
    System.out.println("Predicate.isEqual(null).test(null) = " + Predicate.isEqual(null).test(null));
    System.out.println("Predicate.isEqual(\"jot\").test(\"jot\") = " + Predicate.isEqual("jot").test("jot"));
  }
}

import java.util.function.Predicate;

public class addThen{
  public static void main(String[] args){
    boolean flag = Predicate.not(new Predicate<String>(){
      @Override
      public boolean test(String s){
        return s.contains("jot");
      }
    }).test("jotqw");
    System.out.println("flag = " + flag);
  }
}

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