Primitive to object conversion in Java

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Introduction

Sometimes, you need to use simple values like numbers or letters as objects. This helps when you want to use them in places that only accept objects, like collections.

When you want to store numbers in a list that only accepts objects.

When you need to call methods on a number or character.

When working with APIs that require objects instead of simple values.

When you want to convert a primitive to an object to use in generic classes.

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Syntax

Java

public class WrapperExample {
    public static void main(String[] args) {
        int primitiveInt = 5;
        Integer objectInt = Integer.valueOf(primitiveInt); // Convert int to Integer object

        char primitiveChar = 'a';
        Character objectChar = Character.valueOf(primitiveChar); // Convert char to Character object
    }
}

Java provides wrapper classes like Integer, Character, Double, etc. to convert primitives to objects.

You can also use autoboxing, where Java automatically converts primitives to objects.

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Examples

line_end_arrow_notchConvert primitive int to Integer object explicitly using valueOf method.

Java

int primitiveInt = 10;
Integer objectInt = Integer.valueOf(primitiveInt);

line_end_arrow_notchJava automatically converts primitive int to Integer object (autoboxing).

Java

int primitiveInt = 20;
Integer objectInt = primitiveInt; // Autoboxing

line_end_arrow_notchConvert primitive char to Character object explicitly.

Java

char primitiveChar = 'z';
Character objectChar = Character.valueOf(primitiveChar);

line_end_arrow_notchJava automatically converts primitive char to Character object (autoboxing).

Java

char primitiveChar = 'x';
Character objectChar = primitiveChar; // Autoboxing

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Sample Program

This program shows how to convert primitive int and char values to their object wrappers using both explicit conversion and autoboxing. It prints all values before and after conversion.

Java

public class PrimitiveToObjectConversion {
    public static void main(String[] args) {
        // Primitive int
        int primitiveNumber = 42;
        System.out.println("Primitive int: " + primitiveNumber);

        // Convert primitive int to Integer object explicitly
        Integer objectNumber = Integer.valueOf(primitiveNumber);
        System.out.println("Integer object (explicit): " + objectNumber);

        // Autoboxing: automatic conversion
        Integer autoBoxedNumber = primitiveNumber;
        System.out.println("Integer object (autoboxing): " + autoBoxedNumber);

        // Primitive char
        char primitiveLetter = 'J';
        System.out.println("Primitive char: " + primitiveLetter);

        // Convert primitive char to Character object explicitly
        Character objectLetter = Character.valueOf(primitiveLetter);
        System.out.println("Character object (explicit): " + objectLetter);

        // Autoboxing for char
        Character autoBoxedLetter = primitiveLetter;
        System.out.println("Character object (autoboxing): " + autoBoxedLetter);
    }
}

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Important Notes

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Time complexity: Conversion is very fast, essentially constant time.

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Space complexity: Wrapper objects use more memory than primitives because they store extra information.

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Common mistake: Confusing primitive comparison (==) with object comparison (.equals()). Use .equals() to compare wrapper objects.

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Use primitive to object conversion when you need to store primitives in collections like ArrayList, which only accept objects.

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Summary

Primitive to object conversion lets you use simple values as objects.

Java provides wrapper classes like Integer and Character for this purpose.

Autoboxing makes conversion automatic and easy.