Java学习第三天.note1

数组

平均分

//求总分和平均分        Scanner input = new Scanner(System.in);        double[] array = new double[5];        double sum = 0;        System.out.println("输入成绩");        for (int i = 0; i < array.length; i++) {            array[i] = input.nextDouble();            sum += array[i];        }        System.out.println("总分：" + sum + "平均分：" + sum/5);   

冒泡排序

int[] array = {34,57,26,90,14};//排序，冒泡排序，外层循环的长度n-1,内存循环的长度n-i-1.        int max;        for (int i = 0; i < array.length - 1; i++) {            for (int j = 0; j < array.length - i - 1; j++) {                if(array[j] > array[j + 1]){                    max = array[j];                    array[j] = array[j + 1];                    array[j + 1] = max;                }            }        }        for (int i = 0; i < array.length; i++) {            System.out.println(array[i]);        }

数组的各种方法

排序

//将数组排序，升序        Arrays.sort(array);

复制,二维数组赋初值

int[] array = {34,57,26,90,14};//将源数组从第2个到第5个复制到目标数组，包括第二个，不包括第五个int[] array2 = Arrays.copyOfRange(array, 2, 5);int[] array3 = new int[8];//将源数组从第二个复制到目标数组的第四个位置，复制3个元素System.arraycopy(array, 2, array3, 4, 3);for (int i = 0; i < array3.length; i++) {    System.out.println(array3[i]);}//二维数组,赋初值的几种方式        int[][] array = new int[3][];        array[0] = new int[]{1,3,3,3};        array[1] = new int[]{1,2,3};        array[2] = new int[]{1,2,3,4,5};        int array1[][] = {{1,2,3},{2,3,4},{4,5,6,7}};        for (int i = 0; i < array.length; i++) {            for (int j = 0; j < array[i].length; j++) {                System.out.print(array[i][j] + " ");            }            System.out.println();        }        System.out.println("第二个数组");        for (int i = 0; i < array1.length; i++) {            for (int j = 0; j < array1[i].length; j++) {                System.out.print(array1[i][j] + " ");            }            System.out.println();        }        System.out.println();