Remove specific index from array in java

问题:

Can I remove a specific element from array by mentioning index value? For example can I remove the character d by giving index value 1?

char[] words = { 'c', 'd', 'f', 'h', 'j' };

回答1:

Assuming you do not want your array to contain null values, then you would have to make a method that does it. Something like this should suffice:

public char[] remove(int index, char[] arr) {
    char[] newArr = new char[arr.length - 1];
    if(index < 0 || index > arr.length) {
        return arr;
    }
    int j = 0;
    for(int i = 0; i < arr.length; i++) {
        if(i == index) {
            i++;
        }
        newArr[j++] = arr[i];
    }

    return newArr;
}

Then just replace the old array with the result of remove().

回答2:

If you don't want to use ArrayList, arraycopy is an alternative:

    System.arraycopy(words, 0, result, 0, i);
    System.arraycopy(words, i+1, result, i, result.length-i);

where i is your index to delete.

Hope I can help.

EDIT: Of course you should initially define the correct array lengths:

char[] result = new char[words.length-1];

回答3:

If you need to remove one or multiple elements from array without converting it to List nor creating additional array, you may do it in O(n) not dependent on count of items to remove.

Here, a is initial array, int... r are distinct ordered indices (positions) of elements to remove:

public int removeItems(Object[] a, int... r) {
    int shift = 0;                             
    for (int i = 0; i < a.length; i++) {       
        if (shift < r.length && i == r[shift])  // i-th item needs to be removed
            shift++;                            // increment `shift`
        else 
            a[i - shift] = a[i];                // move i-th item `shift` positions left
    }
    for (int i = a.length - shift; i < a.length; i++)
        a[i] = null;                            // replace remaining items by nulls

    return a.length - shift;                    // return new "length"
}  

Small testing:

Character[] words = {'c','d','f','h','j'};
removeItems(words, 1);
System.out.println(Arrays.asList(words));       // [c, f, h, j, null]

回答4:

You can't remove an element from the array and "reduce" the array size. Once you have created an array, it's length is fixed.

You could change the value to something that has no meaning or is considered "empty", but you can't remove it.
Another option is to use a list, such as an ArrayList. It has a "remove" method that allows you to actually remove the element from it.

回答5:

 import java.util.Arrays;
  public class Main
 {
 public static void main(String[] args) {
 int[] my_array = {25, 14, 56, 15, 36, 56, 77, 18, 29, 49};

 int removeIndex = 1;
 int j=0;
  for(int i = 0; i < my_array.length -1; i++)
  {

    if(i==1)
    {

    }
    else
     {
        my_array[j] = my_array[i];
        j++;
     }

    }
     System.out.println("Original Array : "+Arrays.toString(my_array));   
    }
  }

回答6:

Using String class:

char[] words = { 'c', 'd', 'f', 'h', 'j' };
String str = new String(words);
words = (str.substring(0, Math.min(1, words.length)) + str.substring(Math.min(1 + 1, words.length))).toCharArray();

Running in jshell:

jshell> char[] words = { 'c', 'd', 'f', 'h', 'j' };
words ==> char[5] { 'c', 'd', 'f', 'h', 'j' }

jshell> String str = new String(words);
str ==> "cdfhj"

jshell> words = (str.substring(0, Math.min(1, words.length)) + str.substring(Math.min(1 + 1, words.length))).toCharArray();
words ==> char[4] { 'c', 'f', 'h', 'j' }

jshell>