- Java Generics Tutorial
- Java Generics - Home
- Java Generics - Overview
- Java Generics - Environment Setup
- Examples - Generic Classes
- Java Generics - Generic Classes
- Type Parameter Naming Conventions
- Java Generics - Type inference
- Java Generics - Generic Methods
- Java Generics - Multiple Type
- Java Generics - Parameterized Types
- Java Generics - Raw Types
- Examples - Bounded Type
- Bounded Type Parameters
- Java Generics - Multiple Bounds
- Examples - Collections
- Java Generics - Generic List
- Java Generics - Generic Set
- Java Generics - Generic Map
- Examples - Wild Cards
- Upper Bounded Wildcards
- Generics - Unbounded Wildcards
- Lower Bounded Wildcards
- Generics - Guidelines for Wildcards
- Type Erasure
- Java Generics - Types Erasure
- Java Generics - Bound Types Erasure
- Unbounded Types Erasure
- Java Generics - Methods Erasure
- Restrictions on Generics
- Java Generics - No Primitive Types
- Java Generics - No Instance
- Java Generics - No Static field
- Java Generics - No Cast
- Java Generics - No instanceOf
- Java Generics - No Array
- Java Generics - No Exception
- Java Generics - No Overload
- Java Generics Useful Resources
- Java Generics - Quick Guide
- Java Generics - Useful Resources
- Java Generics - Discussion
Java Generics - Generic Methods Erasure
Java Compiler replaces type parameters in generic type with Object if unbounded type parameters are used, and with type if bound parameters are used as method parameters.
Example
package com.tutorialspoint; public class GenericsTester { public static void main(String[] args) { Box<Integer> integerBox = new Box<Integer>(); Box<String> stringBox = new Box<String>(); integerBox.add(new Integer(10)); stringBox.add(new String("Hello World")); printBox(integerBox); printBox1(stringBox); } private static <T extends Box> void printBox(T box) { System.out.println("Integer Value :" + box.get()); } private static <T> void printBox1(T box) { System.out.println("String Value :" + ((Box)box).get()); } } class Box<T> { private T t; public void add(T t) { this.t = t; } public T get() { return t; } }
In this case, java compiler will replace T with Object class and after type erasure,compiler will generate bytecode for the following code.
package com.tutorialspoint; public class GenericsTester { public static void main(String[] args) { Box integerBox = new Box(); Box stringBox = new Box(); integerBox.add(new Integer(10)); stringBox.add(new String("Hello World")); printBox(integerBox); printBox1(stringBox); } //Bounded Types Erasure private static void printBox(Box box) { System.out.println("Integer Value :" + box.get()); } //Unbounded Types Erasure private static void printBox1(Object box) { System.out.println("String Value :" + ((Box)box).get()); } } class Box { private Object t; public void add(Object t) { this.t = t; } public Object get() { return t; } }
In both case, result is same −
Output
Integer Value :10 String Value :Hello World
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