How to prune out an integer array in Java?

My number is n. n will be the size of the array

int numArray [] = new numArray[N];

However, the contents of the array will hold every other number from 1 to positive n This means that the entire size n array will not be full after the loop Therefore, after the for loop, I want to trim (or resize) the array so that there are no more empty slots in the array

Example:

Assume n = 5; This means that every other number from 1 to 5 will be in the array as follows:

int arr [] = new int [N];

int arr[0]=1;
int arr[1]=3;
int arr[2]= null;
int arr[3]= null;
int arr[4]= null;

Now, I want to trim (or resize) after the for loop so that the null index will disappear, and then the array should be:

int arr[0]=1;
int arr[1]=3;

The size of the array is now 2

Solution

After creation, you cannot change the size of the array in Java

Another important point is that you are creating an array of primitives: int. primitives are not objects, and you cannot assign the value null to primitives If you want to be able to set the entry to null, you need to create a Java Lang. integer array

Integer[] numArray = new Integer[N];

This is a Java function called auto boxing. Almost all code that uses the original int value is also applicable to integer value

pace:

>Use integer [] instead of int [] > calculate the required size (calculate non null entries in the original array) > allocate a new array of the required size > traverse the old array and copy each non null value into the new array

Code:

Integer[] oldArray = ...;

// Step 2
int count = 0;
for (Integer i : oldArray) {
    if (i != null) {
        count++;
    }
}

// Step 3
Integer[] newArray = new Integer[count];

// Step 4
int index = 0;
for (Integer i : oldArray) {
    if (i != null) {
        newArray[index++] = i;
    }
}