在Java利用泛型，呼叫同樣的名稱，回傳不同的類型

使用泛型類別：

public class Test {
    public static void main(String[] args) {
        System.out.println(new DEF<>().bbb(2));
        System.out.println(new DEF<>().bbb("2"));
        System.out.println(new DEF<>().bbb('2'));
    }
}
    
class DEF<T> {
    public T bbb(T c) {
        return new ABC<T>().aaa(c);
    }
}
    
class ABC<T> {
    @SuppressWarnings("unchecked")
    public T aaa(T a) {
        if (a instanceof String) {
            return (T) ((String) a).concat("1");
        } else if (a instanceof Integer) {
            return (T) Integer.valueOf((((Integer) a) + 1));
        }
        return a;
    }
}

也可以使用泛型方法：

public class Test {
    public static void main(String[] args) {
        System.out.println(new DEF().bbb(2));
        System.out.println(new DEF().bbb("2"));
        System.out.println(new DEF().bbb('2'));
    }
}
    
class DEF {
    public <T> T bbb(T c) {
        return new ABC<T>().aaa(c);
    }
}
    
class ABC<T> {
    @SuppressWarnings("unchecked")
    public T aaa(T a) {
        if (a instanceof String) {
            return (T) ((String) a).concat("1");
        } else if (a instanceof Integer) {
            return (T) Integer.valueOf((((Integer) a) + 1));
        }
        return a;
    }
}