Java中实现String.padLeft和String.padRight的示例

System.out.println(String.format("*%1$-10s*", "moon"));
System.out.println(String.format("*%1$10s*", "moon"));

public static String padWhitespaceLeft(String s, int len) {
  return String.format("%1$" + len + "s", s);
}

public static String padWhitespaceRight(String s, int len) {
  return String.format("%1$-" + len + "s", s);
}

System.out.println("*" + padWhitespaceLeft("moon", 12) + "*");
System.out.println("*" + padWhitespaceRight("moon", 12) + "*");

  /**
   * @作者 尧
   * @功能 String左对齐
   */
  public static String padLeft(String src, int len, char ch) {
    int diff = len - src.length();
    if (diff <= 0) {
      return src;
    }

    char[] charr = new char[len];
    System.arraycopy(src.toCharArray(), 0, charr, 0, src.length());
    for (int i = src.length(); i < len; i++) {
      charr[i] = ch;
    }
    return new String(charr);
  }
  /**
   * @作者 尧
   * @功能 String右对齐
   */
  public static String padRight(String src, int len, char ch) {
    int diff = len - src.length();
    if (diff <= 0) {
      return src;
    }

    char[] charr = new char[len];
    System.arraycopy(src.toCharArray(), 0, charr, diff, src.length());
    for (int i = 0; i < diff; i++) {
      charr[i] = ch;
    }
    return new String(charr);
  }

System.out.println("*" + padLeft("moon", 12, '-') + "*");
System.out.println("*" + padRight("moon", 12, '-') + "*");