Java String Starts Wtih startsWith(StringBuilder sb, String prefix)

Description

Tests if this string starts with the specified prefix.

License

LGPL

Parameter

Parameter	Description
prefix	the prefix.

Return

true if the character sequence represented by the argument is a prefix of the character sequence represented by this string; false otherwise. Note also that true will be returned if the argument is an empty string or is equal to this StringBuilder object as determined by comparing the corresponding string obtained by calling the method.

Declaration

public static boolean startsWith(StringBuilder sb, String prefix)

Method Source Code

//package com.java2s;
//License from project: LGPL 

public class Main {
    /**//from  ww w .  j ava  2s  . c om
      * Tests if this string starts with the specified prefix.
      *
      * @param prefix the prefix.
      * @return  <code>true</code> if the character sequence represented by the
      *          argument is a prefix of the character sequence represented by
      *          this string; <code>false</code> otherwise.
      *          Note also that <code>true</code> will be returned if the
      *          argument is an empty string or is equal to this
      *          <code>StringBuilder</code> object as determined by 
      *          comparing the corresponding string obtained by
      *          calling the {@link StringBuilder#toString()} method.
      */
    public static boolean startsWith(StringBuilder sb, String prefix) {
        return startsWith(sb, prefix, 0);
    }

    /**
      * Tests if the substring of the specified <tt>StringBuilder</tt> 
      * beginning at the specified index starts with the specified prefix.
      *
      * @param sb
      * @param prefix the prefix.
      * @param offset where to begin looking in this string.
      * @return  <code>true</code> if the character sequence represented by the
      *          argument is a prefix of the substring of this object starting
      *          at index <code>offset</code>; <code>false</code> otherwise.
      *          The result is <code>false</code> if <code>toffset</code> is
      *          negative or greater than the length of this
      *          <code>StringBuilder</code> object; otherwise the result 
      *          is the same as the result of the expression
      *          <pre>
      *          sb.substring(offset).startsWith(prefix)
      *          </pre>
      */
    public static boolean startsWith(StringBuilder sb, String prefix, int offset) {
        if (offset < 0 || sb.length() - offset < prefix.length())
            return false;

        int len = prefix.length();
        for (int i = 0; i < len; ++i) {
            if (sb.charAt(offset + i) != prefix.charAt(i))
                return false;
        }
        return true;
    }
}