Question

I am Currently learning Generics I have this Generic class here

package generics.lesson;

public class Pair<T> {

    private T first;
    private T second;

    public Pair(){ first = null; second = null; }
    public Pair(T first, T second){ this.first = first ; this.second = second;}

    public T getFirst() { return first; }
    public T getSecond() { return second; }

    public void setFirst(T first) { this.first = first; }
    public void setSecond(T second) { this.second = second; }
}

So far I understand this but then I came across this

public static Pair<String> minmax(String[] a)
    {
        if(a.length == 0 || a == null) return null;
        String min = a[0];
        String max = a[0];

        for(int i = 1 ;  i < a.length ; i++)
        {
            if(min.compareTo(a[i])>0) min = a[i];
            if(max.compareTo(a[i])<0) max  = a[i];
        }
        return new Pair<String>(min,max);
    }

What confuses me is this

public static Pair<String> minmax(String[] a)

QUestion

How is this possible? and can a generic class be a method return type?

Answer 1

If this works

public T getFirst() { return first; } // returns a generic type
public T getSecond() { return second; } // returns a generic type

(which you said you “understand this”)

I would expect this to also work

public static Pair<String> minmax(String[] a) // returns a generic type

BTW: In Java 1.4 neither works, In Java 5.0+ both work. 😉