在for循环中难以从字符串中删除子字符串

Question

I'm trying to work with strings. In my case i have this string:

String test ="/mnt/sdcard/Download/images.jpeg|/mnt/sdcard/Download/images.jpeg|/mnt/sdcard/Download/images-1.jpeg|/mnt/sdcard/Download/images-2.jpeg|";

This string contains 4 paths of images in my android emulator. Every path is separated by the " | " character as you can see. What i want to do is enough simple. I have to create a for loop where i find every single path without the " | " character and on each loop i need to remove the path founded, but in this case with the " | " character. I have implemented the code but i'm not understanding what i'm doing wrong. In fact it remove correctly the image path but not the " | " character. So for example after the first loop the test string become:

|/mnt/sdcard/Download/images.jpeg|/mnt/sdcard/Download/images-1.jpeg|/mnt/sdcard/Download/images-2.jpeg|

that isn't correct because there is the " | " character at the start. Here there is my code.

for(int i=0; i<=3; i++) {
    //find the characters number before you find the first " | " character available
    int indexOfStatic = test.indexOf("|"); 
    //this find the string that we want remove from the test string that contains all paths
    int indexOfStaticToRemove = test.indexOf("|")+1; 

    String testPath = test.substring(0, indexOfStatic); //this is the correct path of the image
    String testPathToRemove = test.substring(0, indexOfStaticToRemove); //this is the path with the " | " character that we want remove from the test string
    Log.i("PATH TO REMOVE",""+testPathToRemove);

    //here i remove the path with the " | " character. I use the replaceFirst method because if the "test" string contains two equals paths (how in my example) i want to replace only one at time for avoid crash during the loop
    test = test.replaceFirst(testPathToRemove,"");
    Log.i("TEST REPLACE",""+test); //Replace the first | with nothing
}

I'm not understanding which is the problem, but in fact it shouldn't be difficult.

Answer 1

You are overlooking in to the problem, use split()

    String[] imagePaths = test.split("\\|");
    for (String string : imagePaths) {
        System.out.println(string);
    }

}

Which gives you the required paths:

    /mnt/sdcard/Download/images.jpeg
    /mnt/sdcard/Download/images.jpeg
    /mnt/sdcard/Download/images-1.jpeg
    /mnt/sdcard/Download/images-2.jpeg

Answer 2

Looks like no one is answering the real question.

Look at the documentation on replaceFirst() method:

http://docs.oracle.com/javase/6/docs/api/java/lang/String.html

It uses regex to replace the part. But | in regex is OR statement. That is causing the confusion you have

Answer 3

You should use the split method:

String[] paths = test.split("\\|");
for (int i=0; i<paths.length; i++) {
  //in paths[i] you have the i-esim path
}

Answer 4

The source of your problem is because of the line:

test = test.replaceFirst(testPathToRemove,"");

Here replaceFirst will take in a regular expression in the first argument, in your case it will be '/mnt/sdcard/Download/images.jpeg|' Note there is a '|' and that '|' will be inferred as an OR operation and hence it can take anything as your string to be replaced. That is why after you execute that line, test will become and empty string.

You can try using substring again instead to get the remaining string.

public static void main(String []args){
    String test = "/mnt/sdcard/Download/images.jpeg|/mnt/sdcard/Download/images.jpeg|/mnt/sdcard/Download/images-1.jpeg|/mnt/sdcard/Download/images-2.jpeg|";
    for(int i=0; i<=3; i++) {
            //find the characters number before you find the first " | " character available
            int indexOfStatic = test.indexOf("|"); 
            //this find the string that we want remove from the test string that contains all paths
            int indexOfStaticToRemove = test.indexOf("|")+1; 

            String testPath = test.substring(0, indexOfStatic); //this is the correct path of the image
            String testPathToRemove = test.substring(0, indexOfStaticToRemove); //this is the path with the " | " character that we want remove from the test string
            System.out.println("PATH: "+testPath);
            System.out.println("PATH TO REMOVE: "+testPathToRemove);


            //here i remove the path with the " | " character. I use the replaceFirst method because if the "test" string contains two equals paths (how in my example) i want to replace only one at time for avoid crash during the loop
            test = test.substring(indexOfStaticToRemove,test.length());
            System.out.println("PATH TO REPLACE: "+test);
            System.out.println();
    }
 }

Answer 5

Yes best option would be use

test.split("\\|") 

and you will get required array or you can use other symbol instead of | ( because it used as OR in regex)in replaceFirst like "#" or "$"

    String test ="/mnt/sdcard/Download/images.jpeg#/mnt/sdcard/Download/images.jpeg#/mnt/sdcard/Download/images-1.jpeg#/mnt/sdcard/Download/images-2.jpeg#";
        for(int i=0; i<=3; i++) {
            //find the characters number before you find the first " | " character available
            int indexOfStatic = test.indexOf("#"); 
            //this find the string that we want remove from the test string that contains all paths
            int indexOfStaticToRemove = test.indexOf("#")+1; 

            String testPath = test.substring(0, indexOfStaticToRemove); //this is the correct path of the image
            String testPathToRemove = test.substring(0, indexOfStaticToRemove); //this is the path with the " | " character that we want remove from the test string
            System.out.println("PATH TO REMOVE"+testPathToRemove);

            //here i remove the path with the " | " character. I use the replaceFirst method because if the "test" string contains two equals paths (how in my example) i want to replace only one at time for avoid crash during the loop
            test = test.replaceFirst(testPathToRemove,"");
            System.out.println("TEST REPLACE"+test); //Replace the first | with nothing

}

it gives following output

PATH TO REMOVE/mnt/sdcard/Download/images.jpeg#
TEST REPLACE/mnt/sdcard/Download/images.jpeg#/mnt/sdcard/Download/images-1.jpeg#/mnt/sdcard/Download/images-2.jpeg#
PATH TO REMOVE/mnt/sdcard/Download/images.jpeg#
TEST REPLACE/mnt/sdcard/Download/images-1.jpeg#/mnt/sdcard/Download/images-2.jpeg#
PATH TO REMOVE/mnt/sdcard/Download/images-1.jpeg#
TEST REPLACE/mnt/sdcard/Download/images-2.jpeg#
PATH TO REMOVE/mnt/sdcard/Download/images-2.jpeg#
TEST REPLACE

Answer 6

test = test.replaceFirst(testPathToRemove,"");

The first parameter in method 'replaceFirst' is not a String, but is a regular expression. As other guys said you can use below code instead of your code. It's very simple.

test.split("\\|");

If you still want to use your code, you can use below code:

test = test.replaceFirst(testPathToRemove.replaceAll("\\|", "\\\\\\|"), "");