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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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