Java 5 的新标准语法和用法详解集锦

Java 5 的新标准语法和用法详解集锦

Java 5 的新标准语法和用法详解集锦

(需要在首选项-java-complier-compiler compliance level中设置为java5.0以上版本)

1,静态导入

1,静态导入
//如import static java.lang.Math.*;
//导入包或类里面的静态方法.

import static java.lang.Math.max;

/**
 * java5的静态导入
 * @author qsuron - 博客:http://blog.csdn.net/qsuron
 */
public class Java5 {
	public static void main(String[] args) {
		System.out.println(max(1,3));
	}
}

2,可变参数的方法:

/**
 * java5的可变参数方法
 * @author qsuron - 博客:http://blog.csdn.net/qsuron
 */
public class Java5 {
	public static void main(String[] args) {
		//实现  x*(x1+x2+x3+...+xn)
		System.out.println(add(2,2,3));//2*(2+3)=10
		System.out.println(add(2,2,3,4,1));//2*(2+3+4+1)=20
	}
	public static int add(int x,int... args){
		int sum = 0;
		for(int i=0;i<args.length;i++){
			sum += args[i];
		}
		return sum*x;
	}
}

3.新增FOR循环:

/**
 * java5的新FOR循环
 * @author qsuron - 博客:http://blog.csdn.net/qsuron
 */
public class Java5 {
	public static void main(String[] args) {
		//实现  x*(x1+x2+x3+...+xn)
		System.out.println(add(2,2,3));//2*(2+3)=10
		System.out.println(add(2,2,3,4,1));//2*(2+3+4+1)=20
	}
	public static int add(int x,int... args){
		int sum = 0;
		for(int i:args){
			sum += i;
		}
		return sum*x;
	}
}

4.用普通类模拟实现枚举类型 & 用java 5的枚举类型用法和设计详解

public class Java5 {
	public static void main(String[] args) {
		Week weekday = Week.MON;
		System.out.println(weekday);
		System.out.println(weekday.nextDay());
	}
}

/**
 * 用普通类模拟实现枚举类型-星期
 * @author qsuron - 博客:http://blog.csdn.net/qsuron
 */
abstract class Week{
	private String conf;
	private Week(String conf){
		this.conf = conf;
	}
	
	/*建立NextDay()抽象方法，将NextDay方法的一堆if...else...转换成为 由子类去覆盖此方法*/
	public abstract Week nextDay();
	
	//建立公开的静态常量子类
	public final static Week MON = new Week("星期一"){
		public Week nextDay() {
			return TUE;
		}
	};
	public final static Week TUE = new Week("星期二"){
		public Week nextDay() {
			return WED;
		}
	};
	public final static Week WED = new Week("星期三"){
		public Week nextDay() {
			return THI;
		}
	};
	public final static Week THI = new Week("星期四"){
		public Week nextDay() {
			return FRI;
		}
	};
	public final static Week FRI = new Week("星期五"){
		public Week nextDay() {
			return STA;
		}
	};
	public final static Week STA = new Week("星期六"){
		public Week nextDay() {
			return SUM;
		}
	};
	public final static Week SUM = new Week("星期日"){
		public Week nextDay() {
			return MON;
		}
	};
	
	/*重写toString()方法*/
	public String toString() {
		return this.conf;
	}
	
}



/**
 * 使用JAVA5提供的枚举类型 - 基础用法和基本方法
 * @author qsuron - 博客:http://blog.csdn.net/qsuron
 */
public class Java5 {
	public static void main(String[] args) {
		Week w = Week.MON;
		System.out.println("toString - "+w);
		System.out.println("与MON比较 - "+w.compareTo(Week.MON));
		System.out.println("Nama - "+w.name());
		System.out.println("所在顺序 - "+w.ordinal());
		System.out.println("枚举数量 - "+Week.values().length);
	}
	public enum Week{
		MON,TUE,WED,THE,FRI,STA,SUM;
	}
}



/**
 * 使用JAVA5提供的枚举类型 - 构造方法
 * 加上private String name  和  重新toString方法可以实现中文信息输出
 * @author qsuron - 博客:http://blog.csdn.net/qsuron
 */
public class Java5 {
	public static void main(String[] args) {
		System.out.println("MON(1),TUE(),WED,THE(1),FRI,STA,SUM();");
		Week w = Week.MON;
		System.out.println(w);
	}
	public enum Week{
		MON(1),TUE(),WED,THE(1),FRI,STA,SUM();
		private Week(){
			System.out.println("空构造函数");
		}
		private Week(int i){
			System.out.println("带参数构造函数");
		}
	}
}


/**
 * 使用JAVA5提供的枚举类型 - 抽象函数
 * 让子类去覆盖抽象方法 - 实现Next()的功能
 * @author qsuron - 博客:http://blog.csdn.net/qsuron
 */
public class Java5 {
	public static void main(String[] args) {
		Week w = Week.MON;
		System.out.println(w.next());
	}
	public enum Week{
		//由于麻烦,只写2个星期数
		MON{
			public Week next(){
				return TUE;
			}
		},
		TUE{
			public Week next(){
				return MON;
			}
		};
		public abstract Week next();
	}
}

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