NetBeans : diamond operator is not supported in -source 1.5 (use -source 7 or higher to enable diamond operator)

Question

I don't know why when I code:

List<String> data = new ArrayList<>();

it said that

diamond operator is not supported in -source 1.5
  (use -source 7 or higher to enable diamond operator)
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(Alt-Enter shows hints)

I already use JDK 1.7. When I opened it in eclipse, I didn't get that error.

Answer 1

-source 1.5 means your code will be compatible with Java version 1.5 and cannot use language constructs introduced later. Read http://docs.oracle.com/javase/8/docs/technotes/tools/unix/javac.html to find more.

Easy way to achieve what you want (to be able to use diamond operator added in Java 7) is to update project source/binary version in project customizer - go to Projects tab (Ctrl-1), select project node, choose Properties in its context menu and update Source/Binary Format field in Source tab.

Answer 2

You missed this:

List<String> data = new ArrayList<String>();

You have to put "String" in both "<>"

Answer 3

right click and choose Properties follow this picture and select new version of source