java-數組的（增刪查）

1.查詢元素

import java.util.Arrays;
import java.util.Scanner;

public class TestArry2 {
    public static void main(String[] args) {
        //數組查詢
        int arr[] = new int[]{12, 34, 55, 11, 151};
        System.out.println(Arrays.toString(arr));
        System.out.println("輸入要查找的數");
        Scanner scanner = new Scanner(System.in);
        int num = scanner.nextInt();
        int index = query(arr, num);
        if (index > 0) {
            System.out.println("索引為" + index);
        } else {
            System.out.println("查無次數");
        }


    }

    public static int query(int arr[], int num) {
        int index = -1;
        for (int i = 0; i <= arr.length - 1; i++) {
            if (arr[i] == num) {
                index = i;
                break;
            }
        }
        return index;
    }
}

2.添加元素

import java.util.Arrays;
import java.util.Scanner;

public class TestArry3 {
    public static void main(String[] args){
    //添加元素
        int arr[]=new int[]{12,43,65,77,11};
        System.out.println(Arrays.toString(arr));

        Scanner scanner=new Scanner(System.in);
        System.out.println("輸入要添加的元素");
        int num=scanner.nextInt();
        System.out.println("輸入要插入的索引位置");
        int n=scanner.nextInt();

        add(arr,n,num);
        System.out.println(Arrays.toString(arr));
    }

    public static  void add(int arr[],int n,int num){
        for (int i=arr.length-1;i>=(n+1);i--){
            arr[i]=arr[i-1];
        }
        arr[n]=num;
    }
}

3.刪除元素

import java.util.Arrays;
import java.util.Scanner;

public class TestArry4 {

    public static void main(String[] args) {
        //刪除元素
        int arr[] = new int[]{12, 34, 56, 77, 100};
        System.out.println(Arrays.toString(arr));
        Scanner scanner = new Scanner(System.in);
        System.out.println("輸入要刪除的元素");
        int num = scanner.nextInt();
        int index = query(arr, num);
        delete(arr, index);
        System.out.println(Arrays.toString(arr));
    }

    //查找索引
    public static int query(int arr[], int num) {
        int index = -1;
        for (int i = 0; i <= arr.length - 1; i++) {
            if (arr[i] == num) {
                index = i;
                break;
            }
        }
        return index;
    }

    //刪除元素
    public static void delete(int arr[], int index) {
        for (int i = index; i <= arr.length - 2; i++) {
            arr[i] = arr[i + 1];
        }
        arr[arr.length - 1] = 0;
    }
}