Java 方法引用 Java 8新特性方法引用仔细讲解

/**
 *   静态方法引用
 * @param <P> 引用方法的参数类型
 * @param <R> 引用方法的返回类型
 */
@FunctionalInterface
interface FunStaticRef<P,R>{

  public R tranTest(P p);

}



public static void main(String[] args) {

    /*
    *  静态方法引用: public static String valueOf
    *   即将String的valueOf() 方法引用为 FunStaticRef#tranTest 方法
    */
    FunStaticRef<Integer, String> funStaticRef = String::valueOf;
    String str = funStaticRef.tranTest(10000);
    System.out.println(str.replaceAll("0", "9"));
}

/**
 *  普通方法引用
 * @param <R> 引用方法返回类型
 */
@FunctionalInterface
interface InstanRef<R>{

  public R upperCase();
}

public static void main(String[] args) {
  
   /*
   * 普通方法的引用: public String toUpperCase()
   *
   */
   String str2 = "i see you";
   InstanRef<String> instanRef = str2 :: toUpperCase;
   System.out.println(instanRef.upperCase());

}

　
/**
 * 特定方法的引用
 * @param <P>
 */
@FunctionalInterface
interface SpecificMethodRef<P>{
  public int compare(P p1 , P p2);
}

public static void main(String[] args) {

   /*
    * 特定方法的引用 public int compareTo(String anotherString)
    *  与之前相比，方法引用前不再需要定义对象，而是可以理解为将对象定义在了参数上！
    */
   SpecificMethodRef<String> specificMethodRef = String :: compareTo;
   System.out.println(specificMethodRef.compare("A","B"));

   ConstructorRef<Book> constructorRef = Book :: new;
   Book book = constructorRef.createObject("Java",100.25);
   System.out.println(book);
}

class Book{
  private String title;
  private double price;

  public Book() {

  }

  public Book(String title,double price){
    this.price = price;
    this.title = title;
  }

  @Override
  public String toString() {
    return "Book{" +"title='" + title + '\'' +", price=" + price +'}';
  }
}



public static void main(String[] args) {

  /*
   * 构造方法引用
   */
  ConstructorRef<Book> constructorRef = Book :: new;
  Book book = constructorRef.createObject("Java",100.25);
  System.out.println(book);
}