18.Arrays类

Arrays类

1.打印数组元素

int[] a = {1,2,3,4,9094,203293,32,311,3};

//利用Arrays工具类，打印数组元素Arrays.toString（）
System.out.println(Arrays.toString(a));

输出:
[1, 2, 3, 4, 9094, 203293, 32, 311, 3]

可以不用自己写方法遍历数组元素再输出。

int[] a = {1,2,3,4,9094,203293,32,311,3};
printArray(a);

//编写方法给主方法调用
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] + "," + " ");
         }
    }
}

输出:
[1, 2, 3, 4, 9094, 203293, 32, 311, 3]

2.数组元素排序

int[] a = {1,2,3,4,9094,203293,32,311,3};

Arrays.sort(a);//默认升序
System.out.println(Arrays.toString(a));

输出:
[1, 2, 3, 3, 4, 32, 311, 9094, 203293]

3.数组填充

int[] a = {1,2,3,4,9094,203293,32,311,3};

Arrays.fill(a ,0);//全填充
System.out.println(Arrays.toString(a));
输出:
[0, 0, 0, 0, 0, 0, 0, 0, 0]

Arrays.fill(a,2,4 ,0);//(a ,fromIndex:2 ,toIndex:4 ,val:0)，部分填充
System.out.println(Arrays.toString(a));
输出:
[1, 2, 0, 0, 4, 32, 311, 9094, 203293]

由下标为2的元素到下标为4的元素填充为0。区间为左闭右开。