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Java Generics - Bound Types Erasure
  • 时间:2024-09-17

Java Generics - Bound Types Erasure


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

Example

package com.tutorialspoint;

pubpc class GenericsTester {
   pubpc 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
", integerBox.get());
      System.out.printf("Double Value :%s
", doubleBox.get());
   }
}

class Box<T extends Number> {
   private T t;

   pubpc void add(T t) {
      this.t = t;
   }

   pubpc 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;

pubpc class GenericsTester {
   pubpc 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
", integerBox.get());
      System.out.printf("Double Value :%s
", doubleBox.get());
   }
}

class Box {
   private Number t;

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

   pubpc Number get() {
      return t;
   }   
}

In both case, result is same −

Output

Integer Value :10
Double Value :10.0
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