Syntax meaning of '< >' in Java

Question

I am manipulating some code and unfortunately I cannot understand this part of it:

public class InMemoryTreeStateManager<T> implements TreeStateManager<T>

What is the meaning of <T>. in this code?

See http://docs.oracle.com/javase/tutorial/java/generics/index.html — home, May 09 '13 at 16:01

score 3 · Answer 1 · edited May 09 '13 at 16:01

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This is a generic. It means T can be any class, and you need to specify what type when you declare a variable of that type. Similar to C++ templates, if you're familiar with that.

edited May 09 '13 at 16:01

Ahmad

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answered May 09 '13 at 16:00

Gabe Sechan

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score 3 · Accepted Answer · answered May 09 '13 at 16:02

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It is generics, it takes some time getting familiar with. you can read more about it here: http://en.wikipedia.org/wiki/Generics_in_Java

answered May 09 '13 at 16:02

Vegard

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score 1 · Answer 3 · answered May 09 '13 at 16:02

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<T> is a generic type. Basically TreeStateManager works with any class that you pass to it, and you can tell it what type of class that is by putting the class name into the braces.

answered May 09 '13 at 16:02

Maloric

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It's the class in the original poster's question using the generic type in braces. – Maloric Mar 31 '14 at 16:42

score 0 · Answer 4 · answered May 09 '13 at 16:02

That's stating InMemoryTreeStateManager is a generic class.

If you would want to instantiate this object (without warnings of raw types) you'd have to give the class a type.

i.e.

InMemoryTreeStateManager<String> manager = new InMemoryTreeStateManager<String>();

Syntax meaning of '< >' in Java

4 Answers4