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3. Methods in Java

Methods are a fundamental part of Java programming, enabling code reusability, modularity, and organization. They are blocks of code that perform a specific task and can be called upon when needed.

1. What is a Method?​

A method is a collection of statements that are grouped together to perform an operation. They can take inputs, perform operations, and return a result.

2. Method Syntax​

The general syntax for defining a method in Java is:

returnType methodName(parameterType parameterName) {
    // Method body
}

Example:​

public int add(int a, int b) {
    return a + b;
}

3. Types of Methods​

3.1. Standard Methods​

  • Instance Methods: Belong to an instance of a class. They can access instance variables and other instance methods.

    public class Calculator {
        public int multiply(int x, int y) {
            return x * y;
        }
    }

  • Static Methods: Belong to the class itself rather than any specific instance. They cannot access instance variables.

    public class MathUtil {
        public static int square(int num) {
            return num * num;
        }
    }

3.2. Constructor Methods​

  • Constructors: Special methods used to initialize objects. They have the same name as the class and do not have a return type.

    public class Person {
        private String name;

        public Person(String name) {
            this.name = name;
        }
    }

3.3. Overloaded Methods​

  • Method Overloading: Allows defining multiple methods with the same name but different parameter types or counts.

    public class Display {
        public void show(int number) {
            System.out.println("Number: " + number);
        }

        public void show(String text) {
            System.out.println("Text: " + text);
        }
    }

3.4. Overridden Methods​

  • Method Overriding: Allows a subclass to provide a specific implementation for a method already defined in its superclass.

    public class Animal {
        public void sound() {
            System.out.println("Animal sound");
        }
    }

    public class Dog extends Animal {
        @Override
        public void sound() {
            System.out.println("Bark");
        }
    }

4. Method Parameters​

Methods can accept parameters, which can be:

  • Formal Parameters: Variables in the method definition.
  • Actual Parameters: Values passed to the method when it is called.

Example:​

public void greet(String name) {
    System.out.println("Hello, " + name);
}

// Calling the method
greet("Alice"); // "Hello, Alice"

5. Return Statement​

A method can return a value using the return statement. If a method has a return type other than void, it must return a value.

Example:​

public int sum(int a, int b) {
    return a + b;
}

6. Varargs (Variable Arguments)​

Java allows you to pass a variable number of arguments to a method using varargs.

Example:​

public void printNumbers(int... numbers) {
    for (int number : numbers) {
        System.out.println(number);
    }
}

// Calling the method
printNumbers(1, 2, 3, 4); // Prints 1 2 3 4

7. Summary of Methods​

FeatureDescription
DefinitionBlock of code performing a specific task.
Return TypesCan return a value or be void (no return).
ParametersCan accept inputs; can be required or optional (varargs).
OverloadingMultiple methods with the same name but different signatures.
OverridingSubclass provides a specific implementation of a superclass method.
Static vs. InstanceStatic methods belong to the class; instance methods belong to an object.