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76

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2

What is the syntax for explicitly giving the type parameters for a generic Java method?

+6  A: 

According to the Java specification that would be for example:

Collections.<String>unmodifiableSet()

(Sorry for asking and answering my own question - I was just looking this up for the third time. :-)

hstoerr
As I understand it answering your own question is perfectly acceptable, as long as it's not a duplicate (i.e. don't go rep-hunting this way).
Joachim Sauer
If it's for posterity, might as well correct the typo in the example ;-).
Mark Peters
+1  A: 

A good example from java.util.Collection of specifying a generic method which defines its own generic type is Collection.toArray where the method signature looks like:

<T> T[] toArray(T[] a);

This declares a generic type T, which is defined on method call by the parameter T[] a and returns an array of T's. So the same instance could call the toArray method in a generic fashion:

Collection<Integer> collection = new ArrayList<Integer>();
collection.add(1);
collection.add(2);

// Call generic method returning Integer[]
Integer[] ints = collection.toArray(new Integer[]{});

// Call generic method again, this time returning an Number[] (Integer extends Number)
Number[] nums = collection.toArray(new Number[]{});

Also, see the java tutorial on generic type parameters.

krock