Java .split不适用于toLowerCase

Question

I want to split a text. I can do it when I use String.split() . For example I split "Hello world." And I get "Hello" and "world" as an output. When I do the same but with toLowerCase I get "hello" and "world." But I don't want this dot after "world". I tried to split with different parameters and put a toLowerCase separately from .split. And I tried to split first and then toLowerCase . Nothing works. What should I do to fade away all these , . ! ? etc. ? Here is how I split:

predlog = main.toLowerCase().split("\\s+");

Answer 1

To keep only the letters and split the rest:

String[] r = main.replaceAll("[^a-zA-Z ]", "").toLowerCase().split("\\s+");

To get rid of all punctuation and split the rest:

String[] r = main.replaceAll("\\p{P}", "").toLowerCase().split("\\s+");

Answer 2

toLowerCase() has no effect on dots.

If you want a simple, but slightly mysterious, fix, also split on dots:

predlog = main.toLowerCase().split("\\s+|\\.");

The reason this works is that split() discards trailing blanks from returned array.

Answer 3

Maybe this answer could help. The code:

String s = "Hello world.";
for (String x : s.toLowerCase().split("[\\p{P} \\t\\n\\r]+"))
    System.out.println(x);

prints out:

> hello
> world

Answer 4

I am sorry, but the reported effect cannot be confirmed. I have tested the reported behaviour with Java 6 and Java 7 as follows:

public static void main(String[] args) {
    String helloWorld = "Hello World.";

    String[] splittedHelloWorld = helloWorld.split("\\s+");
    String[] splittedLowerCaseHelloWorld = helloWorld.toLowerCase().split("\\s+");

    boolean splittedHelloWorldContainsDot = checkContainsDot(splittedHelloWorld);
    boolean splittedLowerCaseHelloWorldContainsDot = checkContainsDot(splittedLowerCaseHelloWorld);

    System.out.println(splittedHelloWorldContainsDot); // true
    System.out.println(splittedLowerCaseHelloWorldContainsDot); // true
}

private static boolean checkContainsDot(String[] splittedArray) {
    boolean containsDot = false;

    for (String string : splittedArray) {
        if (string.contains(".")) {
            containsDot = true;
            break;
        }
    }

    return containsDot;
}