Unary operators in Java - Step-by-Step Execution

Concept Flow - Unary operators

Start

↓

Apply unary operator

↓

Evaluate expression

↓

Update variable if needed

↓

Use result

↓

End

Unary operators take one value, change or use it, then produce a result or update the variable.

Execution Sample

Java

int x = 5;
int y = ++x;
int z = x--;
System.out.println(x + "," + y + "," + z);

This code shows how prefix ++ and postfix -- unary operators change and use variable values.

Execution Table

Step	Expression	Variable x	Variable y	Variable z	Action	Output
1	int x = 5;	5	-	-	Initialize x to 5	-
2	int y = ++x;	6	6	-	Prefix ++ increments x to 6, then y = 6	-
3	int z = x--;	5	6	6	Postfix -- assigns z = 6, then decrements x to 5	-
4	System.out.println(x + "," + y + "," + z);	5	6	6	Print values of x, y, z	5,6,6

💡 All statements executed, program ends.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
x	-	5	6	5	5
y	-	-	6	6	6
z	-	-	-	6	6

Key Moments - 3 Insights

Why does x become 6 before y gets its value in ++x?

Because ++x is prefix increment, it increases x first (step 2), then assigns that new value to y.

Why does z get 6 but x becomes 5 after x--?

Because x-- is postfix decrement, it assigns the current x (6) to z first (step 3), then decreases x to 5.

What is the difference between prefix ++ and postfix -- in this example?

Prefix ++ changes the variable before using it, postfix -- uses the variable first then changes it, as shown in steps 2 and 3.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of x after step 3?

A 7

B 6

C 5

D 4

💡 Hint

Check the 'Variable x' column after step 3 in the execution_table.

At which step does y get its value assigned?

A Step 2

B Step 1

C Step 3

D Step 4

💡 Hint

Look at the 'Action' column for when y is assigned in the execution_table.

If we change ++x to x++, what would be the value of y after step 2?

A 6

B 5

C 7

D 4

💡 Hint

Remember postfix ++ uses the original value before incrementing, check variable_tracker for x changes.

Concept Snapshot

Unary operators use one operand.
Prefix ++ or -- changes value before use.
Postfix ++ or -- uses value then changes it.
Common unary operators: ++, --, +, -, !
They can update variables or produce new values.

Full Transcript

This example shows unary operators in Java. We start with x = 5. Then ++x increases x to 6 before assigning to y, so y becomes 6. Next, x-- assigns current x (6) to z, then decreases x to 5. Finally, printing x, y, z shows 5,6,6. Prefix operators change the variable before use; postfix operators use the variable then change it. This helps understand how unary operators affect variables step-by-step.