java字符串替换函数高效实现

 public static String removeStr(String src, String str) {
         if (src == null || str == null) return src;
         int idx = src.indexOf(str);
         if (idx == -1) return src;
         int pst = 0;
         char[] cs = src.toCharArray();
         char[] rs = new char[src.length() - str.length()];
         for (int i = 0; i < cs.length; i ++) {
             if (i >= idx && i < idx + str.length()) continue;
             rs[pst] = cs[i];
             pst ++;
         }
         return new String(rs);
     }
     public static String replaceStr(String src, String target, String replacement) {
         if (src == null || target == null || replacement == null) return src;
         int idx = src.indexOf(target);
         if (idx == -1) return src;
         int pst = 0;
         char[] cs = src.toCharArray();
         char[] rs = new char[src.length() - target.length() + replacement.length()];
         for (int i = 0; i < cs.length; i ++) {
             if (i == idx) {
                 for (char c : replacement.toCharArray()) {
                     rs[pst] = c;
                     pst ++;
                 }
                 continue;
             }
             if (i > idx && i < idx + target.length()) continue;
             rs[pst] = cs[i];
             pst ++;
         }
         return new String(rs);
     }
     /**
      *
      * @param src
      * @param target
      * @param replacement
      * @return
      */
     public static String replaceAllStr(String src, String target, String replacement) {
         if (src == null || target == null || replacement == null) return src;
         int idx = src.indexOf(target);
         if (idx == -1) return src;
         int pst = 0;
         char[] cs = src.toCharArray();
         char[] rs = new char[src.length() - target.length() + replacement.length()];
         for (int i = 0; i < cs.length; i ++) {
             if (i == idx) {
                 for (char c : replacement.toCharArray()) {
                     rs[pst] = c;
                     pst ++;
                 }
                 continue;
             }
             if (i > idx && i < idx + target.length()) continue;
             rs[pst] = cs[i];
             pst ++;
         }
         return replaceAllStr(new String(rs), target, replacement);
     }