left Pad a string - Java java.lang

Java examples for java.lang:String Pad

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Description

left Pad a string

Demo Code

public class Main {
  public static final String EMPTY = "";

  public static void main(String[] argv) {
    String str = "java2s.com";
    int size = 42;
    String padStr = "+";
    System.out.println(leftPad(str, size, padStr));
  }/* ww  w  .  j av  a  2  s .c o  m*/

  private static final int PAD_LIMIT = 8192;

  private static String padding(int repeat, char padChar) throws IndexOutOfBoundsException {
    if (repeat < 0) {
      throw new IndexOutOfBoundsException("Cannot pad a negative amount: " + repeat);
    }
    final char[] buf = new char[repeat];
    for (int i = 0; i < buf.length; i++) {
      buf[i] = padChar;
    }
    return new String(buf);
  }

  public static boolean isEmpty(String str) {
    return str == null || str.length() == 0;
  }

  public static String leftPad(String str, int size, String padStr) {
    if (str == null) {
      return null;
    }
    if (isEmpty(padStr)) {
      padStr = " ";
    }
    int padLen = padStr.length();
    int strLen = str.length();
    int pads = size - strLen;
    if (pads <= 0) {
      return str; // returns original String when possible
    }
    if (padLen == 1 && pads <= PAD_LIMIT) {
      return leftPad(str, size, padStr.charAt(0));
    }
    if (pads == padLen) {
      return padStr.concat(str);
    } else if (pads < padLen) {
      return padStr.substring(0, pads).concat(str);
    } else {
      char[] padding = new char[pads];
      char[] padChars = padStr.toCharArray();
      for (int i = 0; i < pads; i++) {
        padding[i] = padChars[i % padLen];
      }
      return new String(padding).concat(str);
    }
  }

  public static String leftPad(String str, int size, char padChar) {
    if (str == null) {
      return null;
    }
    int pads = size - str.length();
    if (pads <= 0) {
      return str; // returns original String when possible
    }
    if (pads > PAD_LIMIT) {
      return leftPad(str, size, String.valueOf(padChar));
    }
    return padding(pads, padChar).concat(str);
  }

  public static String substring(String str, int start, int end) {
    if (str == null) {
      return null;
    }

    // handle negatives
    if (end < 0) {
      end = str.length() + end; // remember end is negative
    }
    if (start < 0) {
      start = str.length() + start; // remember start is negative
    }

    // check length next
    if (end > str.length()) {
      end = str.length();
    }

    // if start is greater than end, return ""
    if (start > end) {
      return EMPTY;
    }
    if (start < 0) {
      start = 0;
    }
    if (end < 0) {
      end = 0;
    }
    return str.substring(start, end);
  }

  public static String substring(String str, int start) {
    if (str == null) {
      return null;
    }

    // handle negatives, which means last n characters
    if (start < 0) {
      start = str.length() + start; // remember start is negative
    }
    if (start < 0) {
      start = 0;
    }
    if (start > str.length()) {
      return EMPTY;
    }
    return str.substring(start);
  }

}

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