Java8方法引用及构造方法引用原理实例解析

/**
 * 对象调用实例方法
 */
public static void objMethod(){
  List<Integer> list = new ArrayList<> ();
  list.add(1);
  list.add(2);
  list.add(3);

  list.forEach((i)->{
    PrintStream out = System.out;
    Consumer<Integer> consumer = out::println;
    consumer.accept(i);
  });
  list.forEach(System.out::println);
}

/**
 * 判断两个字符串是否相同
 *
 * @param str1
 * @param str2
 * @return
 */
public static boolean isEqual(String str1, String str2) {
  BiPredicate<String,String> b = (s1,s2)->s1.equals(str2); ①
  BiPredicate<String, String> bp = String::equals;
  return bp.test(str1, str2);
}

/**
 * 比较大小
 * @param x
 * @param y
 * @return
 */
public static boolean compareValue(int x, int y){
  Comparator<Integer> compare = Integer::compare; ②
  return compare.compare(x, y) > 0;
}

public class Apple {
  private String color;
  private double weight;

  public Apple(){

  }
  public Apple(String color) {
    this.color = color;
  }
  public Apple(double weight) {
    this.weight = weight;
  }
  public Apple(String color, double weight) {
    this.color = color;
    this.weight = weight;
  }
  public String getColor() {
    return color;
  }
  public void setColor(String color) {
    this.color = color;
  }
  public double getWeight() {
    return weight;
  }
  public void setWeight(double weight) {
    this.weight = weight;
  }
  @Override
  public String toString() {
    return "Apple{" +
        "color='" + color + '\'' +
        ", weight=" + weight +
        '}';
  }
}

public static void main(String[] args) {
  //无参构造
  //Supplier<Apple> supplier = () -> new Apple(); Lambda表达式写法
  Supplier<Apple> supplier = Apple::new;
  Apple apple = supplier.get();
  System.out.println("NoArgsConstructor: "+apple);

  //有参构造
  //Function<Double,Apple> function = (x) -> new Apple(x);  Lambda表达式写法
  // 构造引用
  Function<Double,Apple> function = Apple::new;
  Apple apply = function.apply(1.0);
  System.out.println("OneArgsConstructor: "+apply);

  BiFunction<String,Double,Apple> bf = Apple::new;
  Apple bi = bf.apply("Red", 2.0);
  System.out.println("TwoArgsConstructor: "+bi);
}

public static <T> T[] initArray(int num, Function<Integer,T[]> function){
  return function.apply(num);
}