Remove multiple substrings from a string - Java

Question

I need to remove multiple substrings from a given String. Example -

String[] exclude = {"one","two","three"};
String input = "if we add one and two we get three"

I want my program to remove all occurrences of "one" or "two" or "three" from the input string and return -

"if we add and we get"

How can i do this in Java ?

Answer 1

Although the question is already answered I was interrested in String replace performance and made a small test. Thus I just add my example code for all who are also interrested in the result. I have written the test in this way that you can also add other replace strategies to test your own.

I have one test driver (no JUnit to make it easier for copy & paste)

public class StringReplaceTest {

    public static void main(String[] args) {
        int iterations = 1000000;

        String[] exclude = { "one", "two", "three" };
        String input = "if we add one and two we get three";

        StringRemove replaceAll = new StringReplaceAll();
        StringRemove replace = new StringReplace();
        StringRemove stringUtilsRemove = new StringUtilsRemove();

        // check if the replacement is implemented correctly
        assertStringRemove(replaceAll);
        assertStringRemove(replace);
        assertStringRemove(stringUtilsRemove);

        profileStringRemove(replaceAll, input, exclude, iterations);
        profileStringRemove(replace, input, exclude, iterations);
        profileStringRemove(stringUtilsRemove, input, exclude, iterations);

    }

    private static void assertStringRemove(StringRemove stringRemove) {
        String[] exclude = { "one", "two", "three" };
        String input = "if we add one and two we get three";
        String replaced = stringRemove.remove(input, exclude);

        String expected = "if we add  and  we get ";
        if (!expected.equals(replaced)) {
            throw new IllegalStateException(
                    "String was not replaced correctly. Excpected <" + expected
                            + "> but was <" + replaced + ">");
        }
    }

    private static void profileStringRemove(StringRemove stringRemove,
            String input, String[] subStringsToRemove, int iterations) {
        long start = System.currentTimeMillis();
        int testCount = iterations;
        while (iterations-- > 0) {
            stringRemove.remove(input, subStringsToRemove);
        }
        long end = System.currentTimeMillis();
        printSummery(stringRemove.getClass().getSimpleName(), testCount, start,
                end);
    }

    private static void printSummery(String action, int iterations, long start,
            long end) {
        System.out.println(action + " took: " + (end - start) + " ms for "
                + iterations + " iterations");
    }

And the different string replace strategies:

public interface StringRemove {

    public String remove(String input, String... subStringsToRemove);
}

public class StringReplaceAll implements StringRemove {

    public String remove(String input, String... subStringsToRemove) {
        for (int ix = 0; ix < subStringsToRemove.length; ix++) {
            input = input.replaceAll(subStringsToRemove[ix], "");
        }
        return input;
    }

}

public class StringReplace implements StringRemove {

    public String remove(String input, String... subStringsToRemove) {
        for (int ix = 0; ix < subStringsToRemove.length; ix++) {
            int replaceLength = 0;
            while (replaceLength != input.length()) {
                input = input.replace(subStringsToRemove[ix], "");
                replaceLength = input.length();
            }
        }
        return input;
    }

}

public class StringUtilsRemove implements StringRemove {

    public String remove(String input, String... subStringsToRemove) {
        for (int ix = 0; ix < subStringsToRemove.length; ix++) {
            input = StringUtils.remove(input, subStringsToRemove[ix]);
        }
        return input;
    }

}

The result on my computer is:

StringReplaceAll took: 3456 ms for 1000000 iterations
StringReplace took: 3162 ms for 1000000 iterations
StringUtilsRemove took: 761 ms for 1000000 iterations