如何使用泛型指定可比较类型的超类关系

Question

I created a method getMax that takes and array of Comparable as a parameter and compares the elements to find the max element, but I also have to implement generics to specify super-class relationships and I do not really understand how I would do that. Below is the src for my non-generic method

public static Comparable getMax(Comparable [] array){
    Comparable max=array[0];
    for(int x=0; x<array.length;x++){
        if(array[x].compareTo(max)==1)
            max=array[x];
    }
    return max;
}

Answer 1

You can rewrite your getMax method with generics like this:

public static <T extends Comparable<T>> T getMax(T[] array){
    T max=array[0];
    for(int x=0; x<array.length;x++){
        if(array[x].compareTo(max)==1)
            max=array[x];
    }
    return max;
}

(You see, the trick is replacing Comparable by T , and declaring T to be Comparable<T> .)

Then, for example you can use it like this:

String[] strings = { "Bob", "Alice", "Charlie" };
String maxString = getMax(strings);  // gives "Charlie"