Convert Object array to Integer array in Java

This post will discuss how to convert the object array to an Integer array in Java.

1. Naive solution

A simple approach is to use a regular for-loop to iterate over the object array, and for every object, we cast it to Integer and assign it to the Integer array.

import java.util.Arrays;

class Main

{

// Program to convert the object array to an Integer array in Java

public static void main(String[] args)

{

Object[] objectArray = { 1, 2, 3, 4, 5 };

Integer[] integerArray = new Integer[objectArray.length];

// copy elements from object array to integer array

for (int i = 0; i < objectArray.length; i++) {

integerArray[i] = (Integer)objectArray[i];

}

System.out.println(Arrays.toString(integerArray));

}

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Output:

[1, 2, 3, 4, 5]

2. Using `System.arraycopy()` method

We can use System.arraycopy() that copies an array from the specified source array, beginning at the specified position, to the specified position of the destination array.

import java.util.Arrays;

class Main

{

// Program to convert the object array to an Integer array in Java

public static void main(String[] args)

{

Object[] src = { 1, 2, 3, 4, 5 };

Integer[] dest = new Integer[src.length];

System.arraycopy(src, 0, dest, 0, src.length);

System.out.println(Arrays.toString(dest));

}

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Output:

[1, 2, 3, 4, 5]

3. Using `Arrays.copyOf()` method

We can also use Arrays.copyOf() to copy the specified array to an array of the specified type.

import java.util.Arrays;

class Main

{

// Program to convert the object array to an Integer array in Java

public static void main(String[] args)

{

Object[] objectArray = { 1, 2, 3, 4, 5 };

Integer[] integerArray = Arrays.copyOf(objectArray,

objectArray.length,

Integer[].class);

System.out.println(Arrays.toString(integerArray));

}

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Output:

[1, 2, 3, 4, 5]

4. Using `List.toArray()` method

Here we first convert the object array to a list of objects and then use the toArray(T[]) method to dump the list into a newly allocated Integer array.

import java.util.Arrays;

class Main

{

// Program to convert the object array to an Integer array in Java

public static void main(String[] args)

{

Object[] objectArray = { 1, 2, 3, 4, 5 };

Integer[] integerArray = Arrays.asList(objectArray)

.toArray(new Integer[0]);

// .toArray(new Integer[objectArray.length]);

System.out.println(Arrays.toString(integerArray));

}

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Output:

[1, 2, 3, 4, 5]

5. Using Java 8

Java 8 provides another simple approach to convert object array to integer array. Following are the steps:

Convert the specified object array to a sequential Stream.
Use Stream.map() to convert every object in the stream to their integer representation.
Use the toArray() method to accumulate the stream elements into a new integer array.

The following program demonstrates it:

import java.util.Arrays;

class Main

{

public static void main(String[] args)

{

Object[] objectArray = { 1, 2, 3, 4, 5 };

// copy elements from object array to integer array

Integer[] integerArray = Arrays.stream(objectArray)

.map(o -> (Integer) o)

.toArray(Integer[]::new);

System.out.println(Arrays.toString(integerArray));

}

Download Run Code

Output:

[1, 2, 3, 4, 5]

That’s all about converting an Object array to an Integer array in Java.

Convert Object array to Integer array in Java

1. Naive solution

2. Using System.arraycopy() method

3. Using Arrays.copyOf() method

4. Using List.toArray() method

5. Using Java 8

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2. Using `System.arraycopy()` method

3. Using `Arrays.copyOf()` method

4. Using `List.toArray()` method