How to delete the last element from an array?

Question

Now I'm working with the recursive backtracking,my assignment is to find the longest path in the maze,the mass is presented as the field covered with the coordinates,and the coordinates of the walls are sore in the file. I have made a parser to parse the input file and build the walls,but I have also stored this coordinates in the array of an object type Coordinate,to check whether it is possible to move the next piece of the "snake" on the next field,then I have created this method,now I have understood that I will need a method to remove the last coordinate from the array when I will use backtracking,how can I do it?the goal is not to use array lists or linked lists only arrays! Thank you!

public class Coordinate {
int xCoord;
int yCoord;

 Coordinate(int x,int y) {
     this.xCoord=x;
     this.yCoord=y;
 }

 public int getX() {
     return this.xCoord;
 }

 public int getY() {
     return this.yCoord;
 }
 public String toString() {
     return this.xCoord + "," + this.yCoord;

 }

 }

And

public class Row {
static final int MAX_NUMBER_OF_COORD=1000;

Coordinate[] coordArray;
int numberOfElements;


Row(){
    coordArray = new Coordinate[MAX_NUMBER_OF_COORD];
    numberOfElements=0;

   }


void add(Coordinate toAdd) {
    coordArray[numberOfElements]=toAdd;
    numberOfElements +=1;
}
boolean ifPossible(Coordinate c1){
    for(int i=0;i<numberOfElements;i++){

        if(coordArray[i].xCoord==c1.xCoord && coordArray[i].yCoord==c1.yCoord){
                return false;
            }
        }


    return true;
}

 }

Is `arrays` use mandatory? You could go with Object variation like `ArrayList` or other giving helpful methods. — Michael Laffargue, Oct 14 '14 at 10:04
Yes it is mandatory,I know it is stupid to use them,but it is mandatory! — Andre Liberty, Oct 14 '14 at 10:05
Use an array long enough and also keep an int variable, size, which contains how many elements of the array are valid. — NomadMaker, Jun 28 '20 at 09:26

score 109 · Answer 1 · edited Jun 28 '20 at 09:12

109

Since in Java, arrays are non-resizable, you will have to copy everything into a new, shorter array.

Arrays.copyOf(original, original.length-1)

edited Jun 28 '20 at 09:12

Naman

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answered Oct 14 '14 at 09:57

Marko Topolnik

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score 1 · Answer 2 · edited Sep 13 '17 at 21:48

I know its a very old thread. Still the approved answer itself didn't work for me. And this is how I resolved it.

Create a method like this:

String[] sliceArray(String[] arrayToSlice, int startIndex, int endIndex) throws ArrayIndexOutOfBoundsException {
    if (startIndex < 0)
        throw new ArrayIndexOutOfBoundsException("Wrong startIndex = " + startIndex);
    if (endIndex >= arrayToSlice.length)
        throw new ArrayIndexOutOfBoundsException("Wrong endIndex = " + endIndex);

    if (startIndex > endIndex) { // Then swap them!
        int x = startIndex;
        startIndex = endIndex;
        endIndex = x;
    }

    ArrayList<String> newArr = new ArrayList<>();
    Collections.addAll(newArr, arrayToSlice);
    for (int i = 0; i < arrayToSlice.length; i++) {
        if (!(i >= startIndex && i <= endIndex)) // If not with in the start & end indices, remove the index
            newArr.remove(i);
    }
    return newArr.toArray(new String[newArr.size()]);
}

Then called it like this:

String lines[] = {"One", "Two", "Three", "Four", "Five"};
lines = sliceArray(lines, 0, 3);

This will result in:

"One", "Two", "Three", "Four"

Now I can slice the array in whichever way I want!

lines = sliceArray(lines, 2, 3);

This will result in:

"Three", "Four"

If you need to specify a start and end possition you should use `Arrays.copyOfRange` — puhlen, Sep 13 '17 at 21:05

score 1 · Answer 3 · answered Feb 13 '22 at 18:29

Well, I found a more efficient option:

System.arraycopy(input, 0, new_array, 0, arr.length - 1);

In a nutshell, this method will copy arr's elements to new_array, without the last element. However this method will require you to create and use another array than the original.

score -1 · Answer 4 · edited Oct 22 '18 at 10:48

-1

    @Test
    public void removeLastElement() {

    String[] lastElementRemoved = { "one", "two", "three" };

    String[] removedElement = Arrays.copyOf(lastElementRemoved, 2);

    System.out.println(Arrays.toString(removedElement));
    }

edited Oct 22 '18 at 10:48

Akshay Paliwal

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answered Oct 22 '18 at 09:52

Mahendra Sri Dayarathna

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How to delete the last element from an array?

4 Answers4

Linked