Erasure of Generic Methods

The Java compiler also erases type parameters in generic method arguments. Consider the following generic method:

// Counts the number of occurrences of elem in anArray.
//
public static <T> int count(T[] anArray, T elem) {
 int cnt = 0;
 for (T e : anArray)
 if (e.equals(elem))
 ++cnt;
 return cnt;
}

Because T is unbounded, the Java compiler replaces it with Object:

public static int count(Object[] anArray, Object elem) {
 int cnt = 0;
 for (Object e : anArray)
 if (e.equals(elem))
 ++cnt;
 return cnt;
}

Suppose the following classes are defined:

class Shape { /* ... */ }
class Circle extends Shape { /* ... */ }
class Rectangle extends Shape { /* ... */ }

You can write a generic method to draw different shapes:

public static <T extends Shape> void draw(T shape) { /* ... */ }

The Java compiler replaces T with Shape:

public static void draw(Shape shape) { /* ... */ }