数组

数组的声明和创建

{
    //变量的类型   变量的名字  =   变量的值
    //数组类型


    public static void main(String[] args) {
        int[] nums;//1.定义

        nums = new int[10];//这里面可以存放10个int类型的数字

        
        //上面两部可以合起来为：int[] nums2 = new int[10];


        nums[0] = 1;
        nums[1] = 2;
        nums[2] = 3;
        nums[3] = 4;
        nums[4] = 5;
        nums[5] = 6;
        nums[6] = 7;
        nums[7] = 8;
        nums[8] = 9;
        nums[9] = 10;

        //计算所有元素的和
        int sum = 0;
        //获取数组长度 ：arrays.length

        for (int i = 0; i< nums.length; i++){
            sum = sum + nums[i];

        }
        System.out.println("总和为："+sum);
    }
}

{
    public static void main(String[] args) {
        int[] arrays = {1, 2, 3, 4, 5};


        //JDK1.5,没有下标
/*        for (int array : arrays) {
            System.out.println(array);

        }*/

        //printArray(arrays);

        int[] reverse = reverse(arrays);
        printArray(reverse);
    }
        //打印数组元素
    public static void printArray(int[] arrays) {
        for (int i = 0; i < arrays.length; i++) {
            System.out.print(arrays[i] + " ");

        }
    }

    //反转数组
    public static int[] reverse(int[] arrays) {
        int[] result = new int[arrays.length];
        
        //反转的操作
        for (int i = 0, j=result.length-1;  i < arrays.length; i++,j--) {
            //result[] = arrays[i];
            result[j] = arrays[i];
        }
        
        return result;
    }


}

二维数组

public static void main(String[] args) {


        //1,2
        //2,3
        //3,4
        //4,5
        int[][] array = {{1,2},{2,3},{3,4},{4,5}};

        //printArray(array[0]);
        System.out.println(array[2][0]);
        System.out.println(array[2][1]);
    }
    public static void printArray(int[] arrays) {
        for (int i = 0; i < arrays.length; i++) {
            System.out.print(arrays[i] + " ");

        }
    }
}

Arrays类讲解

public class Demo06 {
    public static void main(String[] args) {

        int[] a = {1,2,3,4,55555,66852,35548548,525};

        //System.out.println(a);
        //打印数组元素
        //System.out.println(Arrays.toString(a));
        //printArray(a);

        Arrays.sort(a);//数组进行排序，升序

        System.out.println(Arrays.toString(a));

        Arrays.fill(a,2,6,0);//数组填充
        System.out.println(Arrays.toString(a));

    }
    public static void printArray(int[] a){
        for (int i = 0; i < a.length; i++) {
            if (i==0){
                System.out.print("[");
            }
            if (i==a.length-1){
                System.out.print(a[i]+"]");
            }else {
                System.out.print(a[i]+", ");
            }

        }
    }


}