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just like the title said, in Java, is there any difference between the two statements?

Usually I can see the two statements both. So I suppose there may be no difference. But could you help to confirm and explain why they are identical? 

ArrayList<String> al = new ArrayList<String>(); 
ArrayList<String> al = new ArrayList<>();

Thanks!

user2864740
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Zhe Hou
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  • they are identical just two ways of writing. – Panther Sep 11 '15 at 04:33
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    Hi, all, I want to thank you all so much for your answers!! Just mark the first one as acceptable answer, but I think all your answers are clear and correct identically. – Zhe Hou Sep 11 '15 at 06:28

3 Answers3

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They are identical. new ArrayList<String>(); was required prior to JDK 7. In JDK 7 they introduced the 'diamond operator', where the type is inferred.

So, if you are using JDK 7+ you can simply use new Arraylist<>()

You can see this in the Java Language Specification under Class Instance Creation Expressions, or search for 'Diamond Operator'

vman
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In java 7 and later there is no difference. The latter is considered more concise.
The so called diamond operator <> is helping here for the type to be inferred.

George
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This is a Diamond Operator.

The Diamond Operator reduces some of Java's verbosity surrounding generics by having the compiler infer parameter types for constructors of generic classes.

http://www.javaworld.com/article/2074080/core-java/jdk-7--the-diamond-operator.html

Oleksandr Loushkin
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