This topic is about Java Generics – Bound Types Erasure.
Java Compiler replaces type parameters in generic type with their bound if bounded type parameters are used.
Example
package com.Adglob;
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.Adglob;
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
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