Java String拆分无法正常工作

Question

Java Experts ,

Please look into the below split command code and let me know why last two nulls are not captured.

String test = "1,O1,,,,0.0000,0.0000,,";
String[] splittest = test.split(",");
System.out.println("length -"+splittest.length);
for (String string : splittest) {
    System.out.println("value"+string);
}

The result iam getting

length -7
value1
valueO1
value
value
value
value0.0000
value0.0000

surprisingly the length is 7 where as it should be 9 and also as you can see values after 0.0000 ie two last nulls are not coming . Lets say now if i change the string test "1,O1,,,,0.0000,0.0000,0,0"

String test = "1,O1,,,,0.0000,0.0000,0,0";
String[] splittest = test.split(",");
System.out.println("length -"+splittest.length);
for (String string : splittest) {
    System.out.println("value"+string);
}

I am getting correctly

length -9
value1
valueO1
value
value
value
value0.0000
value0.0000
value0
value0

I don't think iam doing wrong . Is it a bug ? JAVA Version - jdk1.6.0_31

Answer 1

It behaves as specified in the javadoc :

This method works as if by invoking the two-argument split method with the given expression and a limit argument of zero. Trailing empty strings are therefore not included in the resulting array.

If you want to keep the trailing blank strings, you can use the 2 argument split method with a negative limit:

String[] splittest = test.split(",", -1);

If the limit is non-positive then the pattern will be applied as many times as possible and the array can have any length.

Answer 2

split silently discards trailing separators, as specified in the Javadoc.

In general, the behavior of split is kind of weird . Consider using Guava's Splitter instead, which has somewhat more predictable and customizable behavior. (Disclosure: I contribute to Guava.)

Splitter.on(',').split("1,O1,,,,0.0000,0.0000,,");
// returns [1, O1, , , , 0.0000, 0.0000, , ]
Splitter.on(',').omitEmptyStrings()
  .split("1,O1,,,,0.0000,0.0000,,");
// returns [1, O1, 0.0000, 0.0000]

Answer 3

As mentioned above, test.split(","); will ignore trailing blank strings. You could use the two parameter method with a large second argument. However, the API also states

If n is non-positive then the pattern will be applied as many times
as possible and the array can have any length.

where n is the second argument. So if you want all the trailing strings, I would recommend

test.split(",", -1);