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.
org.apache.commons.lang.StringUtils.countMatches method could be preferred.
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"));
}
}
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)
one two one and split for one: You get a two-element array: {'', ' two '}. Now your count is 1 although 'one' appears two times in the text.