Java Operators: Types, Subtypes, Rules, Examples & Interview Questions

Java Operators: Types, Subtypes, Rules, Examples & Interview Questions

Operators in Java are symbols that perform operations on variables and values. They are grouped into major types and subtypes.

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1. Arithmetic Operators ➕➖✖️➗ (%)

Subtypes & Rules

Declaration Rule:
Declare numeric types (int, float, double) before using.

int a = 10, b = 3;
int result = a + b;

SDET Interview Q:
Q: What will 10 / 4 output if both are integers?
A: 2 — Integer division truncates decimal.

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2. Relational (Comparison) Operators ⚖️

Subtypes & Rules

Declaration Rule:
Operands must be of the same type or compatible.

int a = 10, b = 5;
boolean result = a > b;

SDET Interview Q:
Q: Difference between == and .equals() on Strings?
A: == checks reference, .equals() checks content.

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3. Logical Operators && || !

Subtypes & Rules

Declaration Rule:
Both operands must be boolean expressions.

boolean result = (age > 18) && (salary > 50000);

SDET Interview Q:
Q: What is short-circuit evaluation?
A: In &&, if first is false, second is skipped. In ||, if first is true, second is skipped.

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4. Assignment Operators 🖊️

Subtypes & Rules

Declaration Rule:
Variable must be declared before usage.

int x = 20;
x += 10; // now x = 30

SDET Interview Q:
Q: Can you use += with Strings?
A: Yes, it acts as string concatenation.

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5. Unary Operators ☝️

Subtypes & Rules

Declaration Rule:
Works on numeric or boolean types.

int x = 5;
int y = ++x; // y = 6, x = 6

SDET Interview Q:
Q: Difference between x++ and ++x in a print statement?
A: x++ prints first, then increments. ++x increments first.

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6. Bitwise Operators ⚙️

Subtypes & Rules

Declaration Rule:
Works only with integer types (int, byte, short, long).

int result = 5 & 3; // 0101 & 0011 = 0001 = 1

SDET Interview Q:
Q: Why use bitwise over logical?
A: Faster, used in performance-critical code or flags.

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7. Ternary Operator ❓

Syntax and Rule:

variable = (condition) ? valueIfTrue : valueIfFalse;

Example:

int a = 10, b = 20;
int max = (a > b) ? a : b;

Declaration Rule:

• Result must match variable type.
• Used only for single conditional expressions.

SDET Interview Q:
Q: Can ternary operator replace if-else?
A: Yes, for simple conditions.

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8. instanceof Operator 🔍

Usage and Rule

Syntax:

object instanceof ClassName

Example:

String name = "John";
if (name instanceof String) {
    System.out.println("It’s a String");
}

Declaration Rule:

• Object must not be null for meaningful result.
• Used for runtime type checking.

SDET Interview Q:
Q: Why is instanceof useful in testing?
A: To verify object types in dynamic PageFactory or polymorphic UI elements.

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9. Type Casting Operators 🔄

Subtypes

Declaration Rule:

• Implicit: Auto-conversion from small to large.
• Explicit: Manual cast needed to avoid data loss.

SDET Interview Q:
Q: What is type casting?
A: Converting one data type to another; explicit casts may lose data...