java - 尝试在 Java 中的数组中创建 AddBefore 方法。不使用ArrayList

Question

public class Arrays {

    private static int[] vals = {1,3,2,5}; 

    public void addBefore(int input, int before){
        int[] temp = new int[vals.length*2];
        //int[] temp2 = new int [vals.length * 2];
        int position = 0; 
        boolean check = false; 
        for(int i = 0; i<vals.length; i++){ 
            check = false; 

            if(vals[i] == (before)){ 
                check = true; 
                temp[i] = input;
                position = i; 
                break; 
            }
            temp[i] = vals[i];
        }

        vals[position] = input; 
        int previous = input; 
        int current = 0; 
        for(int i=position;i<vals.length;i++){
            current = vals[i];
            vals[i] = previous;
            previous = current;
        }   
    }

    public static void main(String[] args){ 
        Arrays a = new Arrays(); 

        a.addBefore(1, 2);
        for(int i = 0; i<vals.length; i++){
            System.out.println(vals[i]);
        }
    }
}

所以我尝试在 Java 中创建一个 addBefore 方法。它有两个参数 input 和 before。我们必须将输入推到给定值之前，而不替换任何内容。当我运行这段代码后。打印出来的数组是{1,3,1,1}。我需要它停止取代并只是插入它前进。

Answer 1

您是否正在寻找这样的东西:

public static int[] addBefore(int[] array, int input, int before)
{
    //create a new array with 1 more space
    int[] newArray = new int[array.length + 1];

    //copy in the original array up to the insertion point
    for (int x = 0; x < before; x++)
    {
        newArray[x] = array[x];
    }

    //element at index 'before' will be pushed one forward; 'before' is now the new one
    newArray[before] = input;

    //fill in the rest
    for (int x = before + 1; x < newArray.length; x++)
    {
        //need to offset it by one to account for the added int
        newArray[x] = array[x - 1];
    }

    return newArray;
}


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

    for(int i = 0; i<vals.length; i++){
        System.out.print(vals[i] + ",");
    }
    System.out.println();

    vals = addBefore(vals, 1, 2);

    for(int i = 0; i<vals.length; i++){
        System.out.print(vals[i] + ",");
    }
}