Bound Types Erasure

Java Compiler replaces type parameters in generic type with their bound if bounded type parameters are used.

Example

package com.tutorialspoint;

public class GenericsTester {
   public static void main(String[] args) {
  Box<Integer> integerBox = new Box<Integer>();
  Box<Double> doubleBox = new Box<Double>();
  integerBox.add(new Integer(10));
  doubleBox.add(new Double(10.0));
  System.out.printf("Integer Value :%d\n", integerBox.get());
  System.out.printf("Double Value :%s\n", doubleBox.get());
   }
}

class Box<T extends Number> {
   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 Number 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 doubleBox = new Box();
  integerBox.add(new Integer(10));
  doubleBox.add(new Double(10.0));
  System.out.printf("Integer Value :%d\n", integerBox.get());
  System.out.printf("Double Value :%s\n", doubleBox.get());
   }
}

class Box {
   private Number t;

   public void add(Number t) {
  this.t = t;
   }

   public Number get() {
  return t;
   }   
}

In both case, result is same −

Output

Integer Value :10
Double Value :10.0