Equality Operators

Question 1

Give all use cases of the equality Operator !

Answer 1

The == operator can compare:

1.Two values of the same primitive type.

2. Two object references (checks if they point to the same object in memory).

When using the equality operator (==) in Java, type compatibility is important. Here’s how it works for the different scenarios :

1. Primitive Types :

Two operands of the same primitive type can be directly compared.

For different primitive types, implicit casting may occur (e.g., comparing int and double, where the int will be promoted to double for the comparison).

2. Object Types:

You can compare two references of the same object type or two compatible types in the class hierarchy.

If the objects are of different types, a compile-time error will occur unless one is a subclass of the other, in which case you can use casting (but you should ensure type safety).

NOTE

Same Primitive Type: Directly comparable.

Different Primitive Types: Implicit casting may occur.
Object References: Must be compatible in type or related through inheritance.

If the types are not compatible, a compile-time error will be raised.

Question 2

What is the difference between the equality and assignement operators ?

Answer 2

The equality operator returns a boolean while the assignement operator returns the value of the left operand

The assignement operator requires from the left operand to be a variable, the equality operator does not

1. Purpose:

Equality Operator (==):

Compares two values or references.

Determines if they are equal, returning a boolean result (true or false).

Assignment Operator (=):

Assigns the value of the right operand to the left operand.

Used to store values in variables.

2. Return Type:

Equality Operator: Returns a boolean value.

Assignment Operator: Returns the value of the right operand after assignment, which can be of any type.

3. Usage:

Equality Operator:

Used in conditional statements, comparisons, and expressions.

Example: if (x == 5) { … }

Assignment Operator:

Used to initialize or update variables.
Example: x = 5;

4. Operand Requirements:

Equality Operator: Can compare any two values or references, regardless of whether they are variables.

Assignment Operator: Requires the left operand to be a variable (or an array element) that can hold a value.

Question 3

What is the difference between equality operator when used with reference types vs when used with primitive types ?

Answer 3

The equality operator (==) behaves differently for reference types and primitive types. For primitive types (like numbers and booleans), it checks for value equality, meaning it compares the actual values. For reference types (like objects), it checks for reference equality by default, meaning it checks if both references point to the same object in memory.

DIFFERENCE

1. Assignment Operator (=):

Primitive Types: Assigns the actual value to a variable. For example, if you assign int a = 5; and then int b = a;, b will have its own copy of the value 5.

Reference Types: Assigns the reference (or pointer) to the object in memory. For instance, if you have Object obj1 = new Object(); and then Object obj2 = obj1;, both obj1 and obj2 will refer to the same object in memory.

2. Equality Operator (==):

Primitive Types: Compares the actual values. For example, 5 == 5 evaluates to true.

Reference Types: Compares references by default, checking if both references point to the same object.

For instance, obj1 == obj2 would return true in the previous example, since they reference the same object. If you wanted to compare the values of the objects, you’d typically need to override the equality method (e.g., equals in Java).