Autoboxing in Java - Step-by-Step Execution

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Concept Flow - Autoboxing

Primitive value

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Autoboxing: Convert to Wrapper Object

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Use Wrapper Object as needed

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Unboxing: Convert back to Primitive (if needed)

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Primitive value ready for operations

Autoboxing automatically converts primitive types to their wrapper objects when needed, and unboxing converts them back.

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Execution Sample

Java

int num = 5;
Integer boxedNum = num; // autoboxing
int unboxedNum = boxedNum; // unboxing
System.out.println(boxedNum);
System.out.println(unboxedNum);

This code shows autoboxing of int to Integer and unboxing back to int, then prints both.

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Execution Table

Step	Action	Variable	Value	Explanation
1	Declare primitive int	num	5	num holds primitive int 5
2	Autoboxing: assign int to Integer	boxedNum	Integer(5)	num is converted to Integer object automatically
3	Unboxing: assign Integer to int	unboxedNum	5	boxedNum is converted back to primitive int
4	Print boxedNum	Output	5	Integer object's value printed as 5
5	Print unboxedNum	Output	5	Primitive int printed as 5
6	End	-	-	Program ends

💡 All steps complete, program ends after printing values.

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Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
num	undefined	5	5	5	5
boxedNum	undefined	undefined	Integer(5)	Integer(5)	Integer(5)
unboxedNum	undefined	undefined	undefined	5	5

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Key Moments - 3 Insights

▶Why can we assign a primitive int directly to an Integer object without explicit conversion?

▶What happens when we assign an Integer object to a primitive int variable?

▶Does printing an Integer object print the object reference or the primitive value?

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Visual Quiz - 3 Questions

Look at the execution_table at step 2. What is the value of boxedNum after autoboxing?

A Primitive int 5

B null

C Integer object holding 5

D String "5"

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Concept Snapshot

Autoboxing in Java:
- Automatically converts primitives (int, double, etc.) to wrapper objects (Integer, Double).
- Happens when assigning primitive to wrapper type.
- Unboxing converts wrapper back to primitive.
- Simplifies code by removing manual conversion.
- Example: Integer i = 5; int n = i;

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Full Transcript

Autoboxing is a Java feature that automatically converts primitive types like int into their wrapper classes like Integer when needed. This means you can assign a primitive int directly to an Integer variable without writing extra code. Similarly, unboxing converts the wrapper object back to a primitive type automatically. In the example, we start with an int variable num set to 5. When we assign num to boxedNum of type Integer, autoboxing converts the int 5 into an Integer object holding 5. Later, when we assign boxedNum back to unboxedNum of type int, unboxing converts the Integer object back to the primitive int 5. Printing both variables shows the value 5. This feature makes code simpler and easier to read by handling conversions behind the scenes.