Exception in thread "main" java.lang.IllegalStateException: stream has already been operated upon or closed
at java.util.stream.AbstractPipeline.<init>(AbstractPipeline.java:203)
at java.util.stream.ReferencePipeline.<init>(ReferencePipeline.java:94)
at java.util.stream.ReferencePipeline$StatelessOp.<init>(ReferencePipeline.java:618)
at java.util.stream.IntPipeline$4.<init>(IntPipeline.java:244)
at java.util.stream.IntPipeline.mapToObj(IntPipeline.java:243)
at java.util.stream.IntPipeline.boxed(IntPipeline.java:220)
at java.util.stream.IntPipeline.distinct(IntPipeline.java:397)
at Ideone.main(Main.java:16)