add an element to int [] array in java [duplicate]

Answer 1

Like others suggested you are better off using collection. If you however for some reason must stick to array then Apache Commons ArrayUtils may help:

int[] series = {4,2};
series = ArrayUtils.add(series, 3); // series is now {4,2,3}
series = ArrayUtils.add(series, 4); // series is now {4,2,3,4};

Note that the add method creates a new array, copies the given array and appends the new element at the end, which may have impact on performance.

Answer 2

import java.util.Arrays;

public class NumberArray {     

    public static void main(String []args){
        int[] series = {4,2};
        int[] newSeries = putNumberInSeries(1,series);
        System.out.println(series==newSeries);//return false. you won't get the same int[] object. But functionality achieved.
    }
    private static int[] putNumberInSeries(int i, int[] series) {
        int[] localSeries = Arrays.copyOf(series, series.length+1);
        localSeries[series.length] = i;
        System.out.println(localSeries);
        return localSeries;
    }
}

Answer 3

The ... can only be used in JDK 1.5 or later. If you are using JDK 4 or lower, use this code:'

public static int[] addElement(int[] original, int newelement) {
    int[] nEw = new int[original.length + 1];
    System.arraycopy(original, 0, nEw, 0, original.length);
    nEw[original.length] = newelement;
}

otherwise (JDK 5 or higher):

public static int[] addElement(int[] original, int... elements) { // This can add multiple elements at once; addElement(int[], int) will still work though.
    int[] nEw = new int[original.length + elements.length];
    System.arraycopy(original, 0, nEw, 0, original.length);
    System.arraycopy(elements, 0, nEw, original.length, elements.length);
    return nEw;
}

Of course, as many have mentioned above, you could use a Collection or an ArrayList, which allows you to use the .add() method.

Answer 4

This works for me:

int[] list = new int[maximum];
for (int i = 0; i < maximum; i++{
    list[i] = put_input_here;
}

This way, it's simple, yet efficient.

Answer 5

The length of an array is immutable in java. This means you can't change the size of an array once you have created it. If you initialised it with 2 elements, its length is 2. You can however use a different collection.

List<Integer> myList = new ArrayList<Integer>();
myList.add(5);
myList.add(7);

And with a wrapper method

public void addMember(Integer x) {
    myList.add(x);
};

Answer 6

You'll need to create a new array if you want to add an index.

Try this:

public static void main(String[] args) {
    int[] series = new int[0];
    int x = 5;


    series = addInt(series, x);

    //print out the array with commas as delimiters
    System.out.print("New series: ");
    for (int i = 0; i < series.length; i++){
        if (i == series.length - 1){
            System.out.println(series[i]);
        }
        else{
            System.out.print(series[i] + ", ");
        }
    }
}

// here, create a method

public static int[] addInt(int [] series, int newInt){
    //create a new array with extra index
    int[] newSeries = new int[series.length + 1];

    //copy the integers from series to newSeries    
    for (int i = 0; i < series.length; i++){
        newSeries[i] = series[i];
    }
//add the new integer to the last index     
    newSeries[newSeries.length - 1] = newInt;



    return newSeries;

     }