8.4 类型变量的限定

class ArrayAlg
{
    public static <T> T min(T[] a) // almost correct
    {
        if (a == null || a.length == 0) return null;
        T smallest = a[0];
        for (int i = 1; i < a.length; i++)
        if (smallest.compareTo(a[i]) > 0) smallest = a[i];
        return smallest;
    }
}

//这样就确保类型T一定有compareTo方法
public static <T extends Comparable> T min(T[] a) . .

//也可以继承多个
T extends Comparable & Serializable