java黑马学习笔记

数组

变量存在栈中，变量值存放在堆中。

数组反转

	public class test{public static void main(String[] args){//目标：完成数组反转int[] arr = {10,20,30,40,50};for (int i = 0,j = arr.length - 1;i < j;i++,j--){int tep = arr[j]; //后一个值赋给临时变量arr[j] = arr[i];//前一个值赋给后一个值arr[i] = tep;//临时变量的值赋给前一个值
}for (int i = 0;i < arr.length;i++){System.out.print(arr[i] + "  " );
}
}
}

随机排名

public class speedkeydemo {public static void main(String[] args) {//目标：完成随机排名int[] codes = new int[5];Scanner sc = new Scanner(System.in);  //定义键盘输入 扫描器for (int i = 0; i < codes.length; i++) {System.out.println("请输入当前第" + (i + 1) + "个员工的工号：");int code = sc.nextInt();codes[i] = code; //对数组赋值}Random r = new Random(); //定义随机数for (int i = 0;i < codes.length;i ++){int index = r.nextInt(codes.length); //返回0 -4 下标int temp = codes[index]; //定义随机变量交换codes[index] = codes[i];codes[i] = temp;//按照随机数打乱数组数据}for (int i = 0; i < codes.length ; i++) {System.out.println(codes[i]+"");}}
}