Splitting a String with the pipe symbol as delimit

问题:

Why is it that in the following, the output is [] and not [1]?

String input="1|2|3";
String[] values= input.split("|");
System.out.println("[" + values[0] + "]");
// Output: []

However, if we change the separator, the output is [1].

String input="1;2;3";
String[] values= input.split(";");
System.out.println("[" + values[0] + "]");
// Output: [1]

回答1:

Try to escape that character:

String input="1|2|3";
String[] values= input.split("\\|");
System.out.println("[" + values[0] + "]");

回答2:

Because the | has special meaning in regular expressions. You need to escape it like this: \| and in Java you also have to escape the backslash as well so you end up with \\|

The pipe character is a disjunction operator which means that it tells the regular expression engine to choose either pattern on the left and right of it. In your case those where empty strings which match anything.

回答3:

The split method receives a regex as a parameter. The pipe is a reserved character with its own purpose (it means or).

You can either escape it ("\\|") or, if you're in Java 1.5+ you can use Pattern.quote("|") like this:

input.split(Pattern.quote("|"));

回答4:

Try using \\| instead of | when you split as you need to escape it.

So your code would change to:

String input="1|2|3";
String[] values= input.split("\\|");
System.out.println("[" + values[0] + "]");

回答5:

you have to escape the character '|' properly

String input="1|2|3";
        String[] values= input.split("\\|");
        System.out.println("[" + values[0] + "]");

回答6:

The pipe character is the equivalent to the logical or in a regex. If you really want to use the pipe character as separator, you need to escape it with a \ as in

String[] values= input.split("\|");