java学习记录--数组

 

 

 

 

package shenhui;
public class code11{
	public static void main(String[] args){
		double bookprice[]=new double [10];
		double bookpricebak[]=bookprice;
		//数组的赋值,只是将bookprice数组的内存地址给了bookpricebak,实际上只有一个数组实例
		double copybookprice[]=new double[bookprice.length];
		double halfbookprice[]=new double[bookprice.length];
		System.out.print("(for循环输出)每本书的价格是");
		for(int a=0;a<bookprice.length;a++){
			//bookprice.length为数组bookprice的长度
			//使用for循环给bookprice中每个元素赋值，也可以使用bookprice[0]=100;这样给每个元素赋值
			//或者int bookprice[]={100,101,102……};数组长度由{}个数决定
			bookprice[a]=100+a;
			//注意此处的a是索引值，索引从0开始
			System.out.print(bookprice[a]+" ");
			//在for循环中打印出每个元素
		}
		System.out.println();
		System.out.print("(for-each输出)每本书的价格是");
		for(double price:bookprice){
			//使用for-each取出数组中的每个元素，for-each不需要像传统for循环般设定初始值、条件式和变量
			//for-each循环会自动将数组中元素由第一个依次取到最后一个
			//此处的price代表的是元素值
			System.out.print(price+" ");
		}
		System.out.println();
		System.out.print("bookpricebak数组内容：");
		for(double i:bookpricebak){
			System.out.print(i+" ");
		}
		System.out.println();
		System.arraycopy(bookprice,0,copybookprice,0,bookprice.length/2);
		//用arraycopy方法完成数组的复制，bookprice与copybookprice有单独的内存地址
		System.out.print("copybookprice数组内容");
		for(double i:copybookprice){
			System.out.print(i+" ");
		}
		System.out.println();
		System.out.print("将bookprice打半价");
		for(int i=0;i<bookprice.length;i++){
			halfbookprice[i]=bookprice[i]*0.5;
			System.out.print(halfbookprice[i]+" ");			
		}
	}
}

 输出结果：

(for循环输出)每本书的价格是100.0 101.0 102.0 103.0 104.0 105.0 106.0 107.0 108.0 109.0 

(for-each输出)每本书的价格是100.0 101.0 102.0 103.0 104.0 105.0 106.0 107.0 108.0 109.0 

bookpricebak数组内容：100.0 101.0 102.0 103.0 104.0 105.0 106.0 107.0 108.0 109.0 

copybookprice数组内容100.0 101.0 102.0 103.0 104.0 0.0 0.0 0.0 0.0 0.0 

将bookprice打半价50.0 50.5 51.0 51.5 52.0 52.5 53.0 53.5 54.0 54.5