（二）冒泡排序

        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入要被排序数组的长度！");
        int len = scanner.nextInt();
        System.out.println("请输入相应长度的数组！");
        int []data = new int[len];
        for (int i = 0; i < len; i++) {
            data[i] = scanner.nextInt();
        }

        for (int i=0, lens = data.length; i < lens - 1; i++) {//lens 在此定义，只会运行一次
            for (int j = 0; j < len - 1 -i; j++) {
                if(data[j] > data[j+1]){
                    //交换 不使用临时变量
                    data[j+1] = data[j+1] + data[j];
                    data[j] = data[j+1] -data[j];
                    data[j+1] = data[j+1] - data[j];
                }
            }
        }

        for (int i = 0; i < len; i++) {
            System.out.print(data[i] + " ");
        }