How to replace slash with underscore

Question

Possible Duplicate:
Hints for java.lang.String.replace problem?
Using string.replace() in Java

Why "/" does not replaced by "_" ?

public static void main(String[] args) throws IOException {
    String file = "A/B";
    file.replaceAll("/", "_");
    System.out.println(file);
}

Answer 1

Because instances of java.lang.String are immutable^*. replaceAll returns the correct string, but your program throws it away. Change your program as follows to correct the issue:

file = file.replaceAll("/", "_");

---

^* That's a fancy way of saying "non-changeable": once a string instance "A/B" is created, there are no methods that you could call on it to change that value.

Answer 2

You need to store the result of the file.replaceAll() call as String instances are immutable:

file = file.replaceAll("/", "_");

Answer 3

You have to assign the result of the replaceAll:

public static void main(String[] args) throws IOException {
    String file = "A/B";
    String newFile = file.replaceAll("/", "_");
    System.out.println(newFile);
}

Answer 4

file.replaceAll("/", "_");

Since, String in Java is immutable, so any method of String class, not just replaceAll, does not modify the existing String.. Rather they create a new String and return that.. So you should re-assign the returned string to the file..

file = file.replaceAll("/", "_");

Answer 5

Look carefully at String.replaceAll javadoc: it returns a String.

Method like this won't modifies their parameter. So you need to write:

String file = "A/B";
file = file.replaceAll("/", "_");

Answer 6

You should read about immutable property.

Immutable property

Why are strings immutable in many programming languages?