Question:

Explain the purpose and syntax of method declaration and invocation in Java.

Answer:

Method Declaration: In Java, a method is a set of instructions that performs a specific action. Method declaration involves defining a method with a name, return type, parameters, and optional access control modifiers and throws clause. The syntax for method declaration is as follows:

<access-modifier> <return-type> methodName(parameter1Type parameter1, parameter2Type parameter2, ...) {
    // Method body
    // Perform specific actions
    return <value>; // Return statement
}

• <access-modifier>: It defines the access level of the method (e.g., public, private, protected).
• <return-type>: It specifies the data type of the value that is returned by the method. If the method does not return any value, the return type is specified as void.
• methodName: It is the name of the method.
• parameter1Type parameter1, parameter2Type parameter2, ... : These are the method parameters, which are the input values passed to the method for processing.

Method Invocation: Invoking or calling a method means executing the code of the method. Method invocation can be done from another method within the same class or from an object of the class where the method is defined. The syntax for method invocation is as follows:

returnType result = methodName(argument1, argument2, ...);

• returnType: It is the data type of the value to be returned by the method. If the method does not return any value, then the returnType is void.
• methodName: It is the name of the method to be invoked.
• argument1, argument2, ...: These are the actual values passed to the method when it is called, corresponding to the parameters defined in the method declaration.

Example:

Suppose we have a method declared as follows:

public int addNumbers(int num1, int num2) {
    int sum = num1 + num2;
    return sum;
}

To invoke the addNumbers method:

int result = addNumbers(5, 7);

In this example, the addNumbers method is invoked with arguments 5 and 7, and the returned value is stored in the variable result.

The method declaration and invocation are essential concepts in Java programming, enabling the modularization of code and reusability of logic.