Lambda expressions are not supported at this language level

Question

I have a Java class that uses Spark. I need to filter out the header from JavaRDD. This is how I want to do this.

String first = data.first();
JavaRDD<String> filteredData = data.filter((String s) -> {return !s.contains(first);});

However, this code data.filter((String s) -> {return !s.contains(first);}) cannot be compiled. IntelliJ IDE says "Lambda expressions are not supported at this language level".

Change your project language level to 8.0. Lambdas don't exist in JDK 7 and earlier. — duffymo, Nov 26 '15 at 12:57

pepyakin · Accepted Answer · 2015-11-26T13:57:43.370

4

You can use lambdas on Java 7, but it is a bit involved — you have to use something like Retrolambda.

Also you can do the same thing without lambdas. Lambdas can be easily represented via annonymous classes, however it is a lot more verbose.

final String first = data.first();
JavaRDD<String> filteredData = data.filter(new Function<String, Boolean>() {
  @Override public Boolean call(String s) {
    return !s.contains(first);
  }
});

edited Nov 26 '15 at 13:57

answered Nov 26 '15 at 12:58

pepyakin

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Could I do a similar thing with Java 7? – Klausos Klausos Nov 26 '15 at 12:58
@KlausosKlausos I updated the answer. – pepyakin Nov 26 '15 at 13:00
What if I don't want to integrate any library in my project? Can I filter out a header using instruments of Java 7? – Klausos Klausos Nov 26 '15 at 13:04
@KlausosKlausos answer updated – pepyakin Nov 26 '15 at 13:11
@KlausosKlausos probably you should also update your question with this requirements. – pepyakin Nov 26 '15 at 13:12
In this case, I assume that variable first must be global? – Klausos Klausos Nov 26 '15 at 13:56
@KlausosKlausos Oops, my bad. `first` should be annotated with `final` in order to be used in anonymous class. – pepyakin Nov 26 '15 at 13:59

Lambda expressions are not supported at this language level

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