Programming Tutorials

substring() in Java

By: Fazal in Java Tutorials on 2007-09-02  

You can extract a substring using substring(). It has two forms. The first is String substring(int startIndex)

Here, startIndex specifies the index at which the substring will begin. This form returns a copy of the substring that begins at startIndex and runs to the end of the invoking string.

The second form of substring() allows you to specify both the beginning and ending index of the substring:

String substring(int startIndex, int endIndex)
Here, startIndex specifies the beginning index, and endIndex specifies the stopping point. The string returned contains all the characters from the beginning index, up to, but not including, the ending index. The following program uses substring() to replace all instances of one substring with another within a string:

// Substring replacement.
class StringReplace {
    public static void main(String args[]) {
        String org = "This is a test. This is, too.";
        String search = "is";
        String sub = "was";
        String result = "";
        int i;
        do { // replace all matching substrings
            i = org.indexOf(search);
            if (i != -1) {
                result = org.substring(0, i);
                result = result + sub;
                result = result + org.substring(i + search.length());
                org = result;
        } while (i != -1);

The output from this program is shown here:

This is a test. This is, too.
Thwas is a test. This is, too.
Thwas was a test. This is, too.
Thwas was a test. Thwas is, too.
Thwas was a test. Thwas was, too.

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