StringUtil.java

package com.cattong.commons.util;

import java.util.Random;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class StringUtil {

	 private static final byte[] CHARS = {
         'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
         'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
         'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
         'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'
	 };


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

    public static boolean isNotEmpty(String str) {
        return !StringUtil.isEmpty(str);
    }

    public static boolean isBlank(String str) {
        int strLen;
        if (str == null || (strLen = str.length()) == 0) {
            return true;
        }
        for (int i = 0; i < strLen; i++) {
            if ((Character.isWhitespace(str.charAt(i)) == false)) {
                return false;
            }
        }
        return true;
    }

    public static boolean isNotBlank(String str) {
        return !StringUtil.isBlank(str);
    }

    public static boolean isEquals(String str1, String str2) {
    	if (str1 == str2) {
    		return true;
    	}
    	if (str1 != null) {
    		return str1.equals(str2);
    	} else {
    		return false;
    	}
    }

	public static boolean isNumeric(String str) {
		if (str == null) {
			return false;
		}
		Pattern pattern = Pattern.compile("[0-9]*");
		Matcher isNum = pattern.matcher(str);
		if (!isNum.matches()) {
			return false;
		}
		return true;
	}
	
    public static int getLengthByByte(String str) {
    	int length = 0;
        if (str == null || str.length() == 0) {
            return length;
        }

        for (int i = 0; i < str.length(); i++) {
            int ascii = Character.codePointAt(str, i);
            if (ascii >= 0 && ascii <= 255) {
                length++;
            } else {
                length += 2;
            }
        }
        return length;
    }

    public static String subStringByByte(String str, int startPos, int length) {
        if (str == null || str.length() == 0) {
            return "";
        }

        StringBuffer sb = new StringBuffer();
        int byteLen = 0;
        for (int i = 0; i < str.length(); i++) {
            int ascii = Character.codePointAt(str, i);
            if (ascii >= 0 && ascii <= 255) {
            	byteLen++;
            } else {
            	byteLen += 2;
            }
            if (byteLen >= startPos + 1 && byteLen <= length) {
            	sb.append(str.charAt(i));
            } else {
            	break;
            }
        }
        return sb.toString();
    }

    public static String getRandomString(int length) {
		Random random = new Random(System.currentTimeMillis());
		byte[] randomBytes = new byte[length];
		for (int i = 0; i < length; i++) {
			randomBytes[i] = CHARS[random.nextInt(CHARS.length)];
		}
		return new String(randomBytes);
	}

    public static String join(Object[] array, String separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    public static String join(Object[] array, String separator, int startIndex, int endIndex) {
        if (array == null) {
            return null;
        }
        if (separator == null) {
            separator = "";
        }

        int noOfItems = (endIndex - startIndex);
        if (noOfItems <= 0) {
            return "";
        }

        StringBuilder buf = new StringBuilder(noOfItems * 16);

        for (int i = startIndex; i < endIndex; i++) {
            if (i > startIndex) {
                buf.append(separator);
            }
            if (array[i] != null) {
                buf.append(array[i]);
            }
        }
        return buf.toString();
    }

}