Common wrapper methods in Java - Step-by-Step Execution

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Concept Flow - Common wrapper methods

Start with primitive value

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Use Wrapper class method

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Method processes value

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Return result (boxed/unboxed/converted)

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Use result in program

Wrapper methods take primitive values, process or convert them, and return results as objects or primitives.

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Execution Sample

Java

int num = 123;
Integer boxed = Integer.valueOf(num);
String str = Integer.toString(num);
int parsed = Integer.parseInt("456");

This code boxes an int, converts it to a string, and parses a string back to int.

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Execution Table

Step	Action	Input	Method Called	Result	Notes
1	Box primitive int to Integer object	123	Integer.valueOf(123)	Integer object with value 123	Boxes int to Integer wrapper
2	Convert int to String	123	Integer.toString(123)	"123"	Returns string representation
3	Parse String to int	"456"	Integer.parseInt("456")	456	Converts string to primitive int
4	Assign parsed int to variable	456	N/A	int 456	Stores parsed value in int variable

💡 All wrapper methods executed, values boxed, converted, and parsed successfully.

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Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
num	123	123	123	123	123
boxed	null	Integer(123)	Integer(123)	Integer(123)	Integer(123)
str	null	null	"123"	"123"	"123"
parsed	uninitialized	uninitialized	uninitialized	456	456

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Key Moments - 3 Insights

▶Why do we use Integer.valueOf() instead of new Integer()?

▶What is the difference between Integer.toString() and String.valueOf()?

▶Why does Integer.parseInt() return a primitive int and not an Integer object?

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Visual Quiz - 3 Questions

Look at the execution_table, what is the type of 'boxed' after step 1?

A Primitive int

B Integer object

C String

D null

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Concept Snapshot

Common wrapper methods:
- Integer.valueOf(int): boxes int to Integer object (may cache)
- Integer.toString(int): converts int to String
- Integer.parseInt(String): parses String to primitive int
Use these to convert between primitives, objects, and strings easily.

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Full Transcript

This visual execution traces common wrapper methods in Java. Starting with a primitive int variable 'num' set to 123, Integer.valueOf(num) boxes it into an Integer object. Then Integer.toString(num) converts the int to its string form "123". Next, Integer.parseInt("456") parses a string to a primitive int 456. Variables change accordingly: 'boxed' holds an Integer object, 'str' holds a string, and 'parsed' holds a primitive int. Key points include why valueOf is preferred over new Integer, differences between toString and valueOf, and parseInt returning primitives. The quiz tests understanding of types and method effects. This helps beginners see how Java wrapper methods work step-by-step.