java 简单数组元素的增删改查

public class Test {
static int[] a = new int[20];
static int n;
public static void main(String[] args) {
int choose;
Scanner sc = new Scanner(System.in);

	System.out.println("请输入初始时存放元素的个数");
	n = sc.nextInt();
	
	System.out.println("请输入元素");
	for(int i=0; i<n; i++){
		a[i] = sc.nextInt();
	}
	
	notice();
	
	while(true){
		switch(choose = sc.nextInt()){
			case 0:
				System.out.println("程序已退出,如需操作请重新运行");
				System.exit(0);
				break;
			case 1:
				System.out.println("你所遍历的元素列表");
				traversal();
				break;
			case 2:
				insertElement();
				traversal();
				break;
			case 3:
				deleteElement();
				traversal();
				break;
			case 4:
				updateElement();
				traversal();
				break;
			default:
				System.out.println("你输入错误,请重新输入");
		}
	}
}


private static void updateElement() {
	int position, elements;

	Scanner sc = new Scanner(System.in);
	System.out.println("请输出要修改元素的位置");
	position = sc.nextInt();
	System.out.println("请输出修改后的元素");
	elements = sc.nextInt();
	
	a[position-1] = elements;
}


private static void deleteElement() {
	int position;
	
	Scanner sc = new Scanner(System.in);
	System.out.println("请输入元素删除的位置");
	position = sc.nextInt();
	
	for(int i=position-1; i<n; i++)
		a[i] = a[i+1];
}


private static void insertElement() {
	int position, elements;

	Scanner sc = new Scanner(System.in);
	System.out.println("请插入元素的位置");
	position = sc.nextInt();
	System.out.println("请插入该位置的元素");
	elements = sc.nextInt();
	
	for(int i=n-1; i>=position-1; i--)
		a[i+1] = a[i];
	a[position-1] = elements; 
}


private static void traversal() {
	for(int i=0; i<n; i++)
		System.out.print(a[i]+" ");
	System.out.println("\n");
	notice();
}


private static void notice() {
	System.out.println("0.退出操作. \n1.遍历元素.  \n2.插入元素.  \n3.删除元素。    \n4.修改元素.");
}

}

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