Method Overloading

1public class Calculator {
2    // Overloading by number of parameters
3    public int add(int a) {
4        return a;
5    }
6    
7    public int add(int a, int b) {
8        return a + b;
9    }
10    
11    public int add(int a, int b, int c) {
12        return a + b + c;
13    }
14}
15
16Calculator calc = new Calculator();
17System.out.println(calc.add(5));        // Output: 5
18System.out.println(calc.add(5, 3));     // Output: 8
19System.out.println(calc.add(5, 3, 2));  // Output: 10

1public class Printer {
2    // Overloading by different parameter types
3    public void print(int value) {
4        System.out.println("Integer: " + value);
5    }
6    
7    public void print(String value) {
8        System.out.println("String: " + value);
9    }
10    
11    public void print(double value) {
12        System.out.println("Double: " + value);
13    }
14    
15    public void print(int[] values) {
16        System.out.println("Array: " + Arrays.toString(values));
17    }
18}
19
20Printer p = new Printer();
21p.print(42);          // Integer: 42
22p.print("Hello");     // String: Hello
23p.print(3.14);        // Double: 3.14
24p.print(new int[]{1,2,3}); // Array: [1, 2, 3]

1// Type Promotion in Overloading
2public class TypePromotion {
3    public void show(int a) {
4        System.out.println("int: " + a);
5    }
6    
7    public void show(double a) {
8        System.out.println("double: " + a);
9    }
10}
11
12TypePromotion tp = new TypePromotion();
13tp.show(10);    // int: 10 (exact match)
14tp.show(10.5);  // double: 10.5 (exact match)
15tp.show('A');   // int: 65 (char promoted to int!)
16tp.show(10L);   // double: 10.0 (long promoted to double)
17
18// Ambiguity Example - WON'T COMPILE
19// public void ambiguous(int a, long b) {}
20// public void ambiguous(long a, int b) {}
21// ambiguous(5, 5); // ERROR: Ambiguous!

1// Real-world: StringBuilder append() overloading
2StringBuilder sb = new StringBuilder();
3sb.append("Hello");      // append(String)
4sb.append(42);           // append(int)
5sb.append(true);         // append(boolean)
6sb.append('!');          // append(char)
7sb.append(3.14);         // append(double)
8sb.append(new int[]{1}); // append(Object)
9
10// Real-world: Constructor overloading
11public class User {
12    private String name;
13    private int age;
14    
15    public User() {                    // No-arg constructor
16        this("Unknown", 0);
17    }
18    
19    public User(String name) {         // One-arg constructor
20        this(name, 0);
21    }
22    
23    public User(String name, int age) { // All-args constructor
24        this.name = name;
25        this.age = age;
26    }
27}