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java-8nashorn

why Character.digit output in java8 jjs shell is not correct

Use java8 jjs to study jdk api and found this, see below:

jjs> var result = java.lang.Character.digit('473'.charAt(0),10)
jjs> result
-1
jjs> '473'.charAt(0)
4

but if I executed above code in java main, got 4.

System.out.println(Character.digit('4', 10));//4

why in jjs it returns -1?

Solution

  • This has to do with the automatic resolution of Java methods. Since a char is internally represented as an int, Nashorn will resolve the digit method as the one accepting a Unicode codePoint (int) and radix.

    If you want to make sure to call the digit method that accepts a character (char) and radix, you should explicitly resolve the method you want to invoke, like this:

    $ jjs
jjs> var digit = java.lang.Character['digit(char,int)']
jjs> digit('473'.charAt(0), 10)
4