java 8 新特征

    一   接口中实现方法：

    （1）用修饰符static修饰方法

    定义：

public interface IMessage {
	      static int add(int a,int b){
		     	return a + b;
	      }
}

    调用：

public static void main(String[] args) {
		int a = 3,
				b = 3;
		int add = IMessage.add(a, b);
		System.out.println(add);
	}

   （2）用修饰符default 修饰方法

    定义

public interface IMessage {
	      default int add(int a,int b){
		     	return a + b;
	      }
}

    实现

public class IMessageImpl implements IMessage {
	
}

   调用：

public static void main(String[] args) {
		IMessage iMessage = new IMessageImpl();
		int a = 1, b = 9;
		int c = iMessage.add(a, b);
		System.out.println(c);
	}

 (二)lamde表达式

    匿名函数

package com.java.demo;

public class TestDemo {

	public interface IMessage {
		public void print();
	}

	public static void main(String[] args) {
		fun(new IMessage() {
			@Override
			public void print() {
                     System.out.println("Hello！");
			}
		});
	}

	public static void fun(IMessage msg) {
		msg.print();
	}

}

 Lamde表达式主要用于解决匿名函数的繁琐

  

package com.java.demo;

public class TestDemo {

	public interface IMessage {
		public void print();
	}

	public static void main(String[] args) {
		fun(()->System.out.println("Hello！"));
	}

	public static void fun(IMessage msg) {
		msg.print();
	}

}

 Lamda 表达式语法

（1）（参数）->单行语句

package com.java.demo;

public class TestDemo {

	public interface IMessage {
		public void print(String arg);
	}

	public static void main(String[] args) {
		fun((arg)->System.out.println(arg));
	}

	public static void fun(IMessage msg) {
		msg.print("Hello!");
	}

}

 

（2）（参数）->{代码块}

package com.java.demo;

public class TestDemo {

	public interface IMessage {
		public void print(String arg);
	}

	public static void main(String[] args) {
		fun((arg)->{
		    	arg = arg.toLowerCase();
			    System.out.println(arg);
			});
	}

	public static void fun(IMessage msg) {
		msg.print("HELLO!");
	}

}

 

（3）（参数）->表达式

package com.java.demo;

public class TestDemo {

	public interface IMessage {
		public int print(int x, int y);
	}

	public static void main(String[] args) {
		fun((x,y)-> x+y );
	}

	public static void fun(IMessage msg) {
		System.out.println(msg.print(1,2));
	}
}

 （三）方法的引用

（1）引用静态方法：类名称::static 方法名；

package com.java.demo;

public class TestDemo {

	public interface IMessage<P,R> {
		public R  header(P p);
	}

	public static void main(String[] args) {
         IMessage<Integer,String> msg  =	String::valueOf;
         String arg = msg.header(1000);
         System.out.println(arg);
	}

}

 

（2）引用对象的方法::实例化对象::普通方法；

package com.java.demo;

public class TestDemo {

	public interface IMessage<P> {
		public boolean  header(P p);
	}

	public static void main(String[] args) {
         IMessage<String> msg  ="wewe"::equals;
         boolean header = msg.header("wewe");
         System.out.println(header);
	}

}

 

（3）引用特定类型的方法：特定类::普通方法；

package com.java.demo;

public class TestDemo {

	public interface IMessage<P> {
		public boolean  header(P p,P r);
	}

	public static void main(String[] args) {
         IMessage<String> msg  =String::equals;
         boolean header = msg.header("wewe","wewe");
         System.out.println(header);
	}

}

 

 

（4）引用构造方法：类名称::new;

 

package com.java.demo;

interface IMessage<P>{
	public P create(String name,int age);
}

class Student{
	private String name;
	private int age;
	public Student (String name ,int age){
		   this.name=name;
		   this.age = age ;
	}
	
	public String toString(){
		return "姓名："+ this.name + "年齡："+this.age;
	}
	
} 


public class TestDemo {
	public static void main(String[] args) {
	    IMessage<Student> msg =   Student::new;
	    Student student = msg.create("張志東", 27);
	    System.out.println( student.toString()); 
	
	}

}