Type Erasure

---

Edit the material here!

What happens when your Java generics code compiles

#This is a brief summary of type erasure that takes references from Javadocs, https://docs.oracle.com/javase/tutorial/java/generics/erasure.html as well as lectures provided in the module.

When Java compiler compiles your code into bytecode, it has to convert the parameterised types into an appropriate type.

• Unbounded Parameterised Types are converted into Object type
• Bounded Parameterised Types are converted into its bounds

Here's some example of code:

class Example<T> {
  private T details;
  
  Example(T details) {
    this.details = details;
  }
  public void giveClarity(T furtherDetails) {
    this.details = furtherDetails;
  }
}

class BetterExample extends Example<String> {
  
  BetterExample(String details) { super(details); }
  
  public void giveClarity(String furtherDetails) { this.details = furtherDetails; }
  
}

In this case, when compiling, all the type parameter T in class Example is converted to Object type.

But lets consider something more... After compiling, the giveClarity method takes in an Object in class Example and a String in class BetterExample. And hence overriding is not explicitly taking place due to the difference in method signatures. Hence, Java compiler creates a bridge method to serve the purpose of overriding and polymorphism.

class BetterExample extends Example<String> {
  
  BetterExample(String details) { super(details); }
  
  // Bridge Method generated by Java Compiler
  public void giveClarity(Object furtherDetails) { giveClarity( (String) furtherDetails); } 
  
  public void giveClarity(String furtherDetails) { this.details = furtherDetails; }
  
}

And this is what happens after we write a piece of code that involves the use of generics. :smiley