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stringsubstringjava-6
Unknown user
Unknown user

Reputation: 45301

Finding sub-strings in Java 6

I looked through the String API in Java 6 and I did not find any method for computing how many times a specific sub-string appears within a given String.

For example, I would like to know how many times "is" or "not" appears in the string "noisxxnotyynotxisi".

I can do the long way with a loop, but I would like to know whether there is a simpler way.

Thanks.

Edit: I'm using Java 6.

Upvotes: 0

Views: 238

Answers (3)

Buhake Sindi
Buhake Sindi

Reputation: 89169

Without using an external library, you can use String.indexOf(String str, int fromIndex); in a loop.

Update This example fully works.

/**
 * @author The Elite Gentleman
 * @since 31 March 2011
 *
 */
public class Test {

    private static final String STR = "noisxxnotyynotxisi";

    public static int count(String str) {
        int count = 0;
        int index = -1;

        //if (STR.lastIndexOf(str) == -1) {
        //  return count;
        //}

        while ((index = STR.indexOf(str, index + 1)) != -1) {
            count++;
        }

        return count;
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println(Test.count("is"));
        System.out.println(Test.count("no"));
    }
}

Upvotes: 2

Peter Lawrey
Peter Lawrey

Reputation: 533442

You can do this, but a loop would be faster.

String text = "noisxxnotyynotxisinono";
String search = "no";
int count = text.split(search,-1).length-1;

System.out.println(Arrays.toString(text.split(search,-1)));
System.out.println("count= " + count);

prints

[, isxx, tyy, txisi, , ]
count= 5

As you can see this is correct if the text starts or ends with the search value. The -1 argument stops it removing trailing seperators.

You can use a loop with indexOf() which is more efficient, but not as simple.

BTW: Java 5.0 has been EOL since Aug 2007. Perhaps its is time to look at Java 6. (though the docs are very similar)

Upvotes: 0

Gursel Koca
Gursel Koca

Reputation: 21280

org.apache.commons.lang.StringUtils.countMatches method could be preferred.

Upvotes: 4

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