Java generic methods and type qualification

generic methods can be defined in a normal class or in a generic class

1 class arrayalg{2      Public static <T> T getmiddle (t...a) {3         return a[a.length/2]; 4     }5 }

Note: Type variables are placed after modifiers (public static)when a generic method is called, the method name is placed in a specific type before the angle brackets

String middle=arrayalg.<string>getmiddle ("John", "Q.", "public");

in most cases, the method call can omit the <String> type parameter

String middle=arrayalg.getmiddle ("John", "Q.", "public");

qualification of type variablessometimes a class or method needs to constrain a type variable

1 classarrayalg{2      Public Static<T>T min (t[] a) {3         if(a==NULL|| a.length==0)return0;4T smallest=a[0];5          for(inti=1;i<a.length;i++)6             if(Smallest.compareto (A[i]) >0)7smallest=A[i];8             returnsmallest;9     }Ten}

in the example above, the variable smallest type is T, and the smallest must have a CompareTo method to run properlythe workaround is to limit t implementation of the comparable interface

 Public Static extends comparable> T min (t[] a) ...

a type variable or wildcard can have more than one qualification, with a qualified type of & delimited

extends Comparable & Serializable

Java generic methods and type qualification