Reference data types in Java - Step-by-Step Execution

Concept Flow - Reference data types

Declare reference variable

↓

Assign object to variable

↓

Variable points to object in memory

↓

Use variable to access object data/methods

↓

Change variable to point to another object or null

↓

Old object may be garbage collected if no references

Reference variables hold addresses to objects in memory, not the actual data. They let you access and manipulate objects indirectly.

Execution Sample

Java

String name = "Alice";
String another = name;
name = "Bob";
System.out.println(another);

This code shows how reference variables point to objects and how changing one variable does not affect the other.

Execution Table

Step	Action	Variable 'name'	Variable 'another'	Output
1	Declare and assign "Alice" to name	"Alice" object	null
2	Assign name to another	"Alice" object	"Alice" object
3	Change name to "Bob"	"Bob" object	"Alice" object
4	Print another	"Bob" object	"Alice" object	Alice
5	End	"Bob" object	"Alice" object

💡 Program ends after printing 'Alice', showing 'another' still points to original object

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
name	null	"Alice"	"Alice"	"Bob"	"Bob"
another	null	null	"Alice"	"Alice"	"Alice"

Key Moments - 2 Insights

Why does printing 'another' show 'Alice' even after 'name' changes to 'Bob'?

Because 'another' points to the original "Alice" object, and changing 'name' to "Bob" makes 'name' point to a new object, not affecting 'another' (see execution_table step 4).

Does assigning one reference variable to another copy the object?

No, it copies the reference (address), so both variables point to the same object initially (see execution_table step 2).

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what does variable 'name' point to?

A null

B "Alice" object

C "Bob" object

D Same as 'another'

💡 Hint

Check the 'Variable name' column at step 3 in execution_table

At which step does 'another' get assigned a value?

A Step 2

B Step 3

C Step 1

D Step 4

💡 Hint

Look at the 'Action' column describing assignment to 'another' in execution_table

If we changed 'name' to point to null at step 3, what would 'another' point to?

A null

B "Alice" object

C "Bob" object

D It would cause an error

💡 Hint

Variable 'another' keeps its reference unless explicitly changed (see variable_tracker)

Concept Snapshot

Reference data types hold addresses to objects, not the data itself.
Assigning one reference to another copies the address, not the object.
Changing one reference variable to a new object does not affect others.
Objects without references can be removed by garbage collection.

Full Transcript

In Java, reference data types store addresses pointing to objects in memory. When you assign one reference variable to another, both point to the same object. Changing one variable to point to a new object does not change the other. For example, if 'name' points to "Alice" and 'another' is assigned 'name', both point to the same "Alice" object. Changing 'name' to "Bob" makes 'name' point to a new object, but 'another' still points to "Alice". This shows how references work differently from simple data copies.