Java中一些常用的方法实现（更新中）

一、数组

1、indexOf

int targetIndex = indexOf(arr, targetValue);

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

2、formatArray

    public static void formatArray(int[] arr){
        for (int i = 0; i < arr.length; i++){
            if(i == 0){
                System.out.print("[" + arr[i] +",");
            }
            else if(i != arr.length - 1){
                System.out.print(arr[i] + ",");
            }else{
                System.out.print(arr[i]+"]");
            }
        }
        System.out.println('\n');
    }

3、addItem(根据索引)

    public static int[] addItem(int[] arr,int index,int value){
        System.out.println("将在该数组中的第" + index + "个位置添加" + value);
        for(int i = arr.length - 1; i >= index; i--){
            arr[i] = arr[i - 1];
        }
        arr[index - 1] = value;
        return arr;
    }

4、deleteItem(根据索引)

    public static int[] deleteItem(int[] arr,int index){
        for(int i = index-1; i<arr.length-1; i++){
            arr[i] = arr[i+1];
        }
        arr[arr.length-1] = 0;
        int[] newArr = new int[arr.length-1];
        for(int i = 0; i < newArr.length; i++){
            newArr[i] = arr[i];
        }
        return newArr;
    }