A Generic Method is a method that can operate on different types of data. Instead of hardcoding a data type, it uses a type parameter (like <T>) to define the type when the method is called.
Generic methods allow for:
-
Code reuse
-
Compile-time type safety
-
No need for casting
Syntax
public <T> void methodName(T parameter) {
// Method body
}
<T> is a type parameter declaration placed before the return type.
You can use any valid identifier (T, E, K, V are conventional).Code language: PHP (php)Program-1: Simple Generic Method
public class Utility {
// Generic method to print any type
public static <T> void printItem(T item) {
System.out.println("Item: " + item);
}
public static void main(String[] args) {
printItem("LotusJavaPrince");
printItem(100);
printItem(55.5);
}
}
/*
Item: LotusJavaPrince
Item: 100
Item: 55.5
*/Example 2: Generic Method with Arrays
public class ArrayPrinter {
// Generic method to print elements of any array
public static <T> void printArray(T[] array) {
for (T element : array) {
System.out.print(element + " ");
}
System.out.println();
}
public static void main(String[] args) {
Integer[] intArray = {1, 2, 3};
String[] strArray = {"Lotus", "Java", "Prince"};
printArray(intArray);
printArray(strArray);
}
}
/*
1 2 3
Lotus Java Prince
*/Example 3: Bounded Type Parameters in Generic Methods
public class Calculator {
// Generic method to find the maximum of two numbers
public static <T extends Number> double add(T a, T b) {
return a.doubleValue() + b.doubleValue();
}
public static void main(String[] args) {
System.out.println(add(10, 20)); // int
System.out.println(add(5.5, 4.5)); // double
}
}
/*
30.0
10.0
*/Example 4: Generic Method with Multiple Type Parameters
public class PairPrinter {
// Generic method with two type parameters
public static <K, V> void printPair(K key, V value) {
System.out.println("Key: " + key + ", Value: " + value);
}
public static void main(String[] args) {
printPair("EmployeeID", 1001);
printPair(200, "Mahesh");
}
}
/*
Key: EmployeeID, Value: 1001
Key: 200, Value: Mahesh
*/Example 5: Generic Method with Custom Objects (e.g., Employee)
public class Employee {
String name;
int id;
public Employee(String name, int id) {
this.name = name;
this.id = id;
}
@Override
public String toString() {
return "Employee[ID=" + id + ", Name=" + name + "]";
}
}
public class Display {
// Generic method
public static <T> void showDetails(T obj) {
System.out.println("Details: " + obj);
}
public static void main(String[] args) {
Employee emp = new Employee("LotusJavaPrince", 101);
showDetails(emp);
showDetails("Generic Example");
}
}
/*
Details: Employee[ID=101, Name=LotusJavaPrince]
Details: Generic Example
*/