一道截取字符串的题目
今天在搜索判断字符是否是中文的时候看到一道面试题目：
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public static boolean isChinseseChar(char ch) {Pattern p = Pattern.compile("[\\u4e00-\\u9fa5]");return p.matcher(ch+"").find();}/** * 编写一个截取字符串的函数，输入为一个字符串和字节数，输出为按字节截取的字符串。 * 但是要保证汉字不被截半个，如“我ABC”4，应该截为“我AB”，输入“我ABC汉DEF”，6，应该输出为“我ABC”而不是“我ABC+汉的半个”。 * @param source 源字符串 * @param startPos 开始字节数 * @param endPos 结束字节数 * @param charset 编码类型 * @return 截取的字符串 * @throws UnsupportedEncodingException */public static String cutString(String source,int startPos, int endPos, String charset) throws UnsupportedEncodingException{byte[] bs = source.getBytes(charset);if(startPos > bs.length)throw new RuntimeException("startPos大于字符" + source + "的总共字节数!");if(endPos > bs.length)endPos = bs.length;int offset = 0;int factor = "编".getBytes(charset).length;int start = -1, end = -1;for(int i=0; i<source.length(); i++) {if(offset == startPos)//offset = startPos，其实位置的字节数正好是一个非中文字开头start = i;if(offset > startPos && start == -1)//offset已经大于startPos但是还没找到offset=startPos的位置，说明开始的是一个中文字符start = i;if(isChinseseChar(source.charAt(i)))offset += factor;else offset ++;if(offset == endPos){end = i+1;}if(offset > endPos && end == -1) {end = i;}if(start != -1 && end != -1)break;}if(start >= end)return "";return source.substring(start,end);}public static String cutString(String source,int startPos,int endPos) throws UnsupportedEncodingException{return cutString(source,startPos,endPos,Charset.defaultCharset().toString());}public static String cutString(String source,int endPos) throws UnsupportedEncodingException{return cutString(source,0,endPos,Charset.defaultCharset().toString());}public static String cutString(String source,int endPos, String charset) throws UnsupportedEncodingException{return cutString(source,0,endPos,charset);}/** * @param args * @throws IOException */public static void main(String[] args) throws IOException {String source = "我是abc";System.out.println(source+"[0,4](gbk): "+cutString(source,0,4,"gbk"));System.out.println(source+"[0,4](utf-8): "+cutString(source,0,4,"utf-8"));source = "adf12我是abc";System.out.println(source+"[0,2](gbk): "+cutString(source,0,2,"gbk"));System.out.println(source+"[0,2](utf-8): "+cutString(source,0,2,"utf-8"));source = "add她fdf2我是abc";System.out.println(source+"[0,11](gbk): "+cutString(source,0,11,"gbk"));System.out.println(source+"[0,11](utf-8): "+cutString(source,0,11,"utf-8"));System.out.println(source+"[10,11](gbk): "+cutString(source,10,11,"gbk"));System.out.println(source+"[10,11](utf-8): "+cutString(source,10,11,"utf-8"));System.out.println(source+"[8,12](gbk): "+cutString(source,8,12,"gbk"));System.out.println(source+"[8,12](utf-8): "+cutString(source,8,12,"utf-8"));System.out.println(source+"[9,11](gbk): "+cutString(source,9,11,"gbk"));System.out.println(source+"[9,11](utf-8): "+cutString(source,9,11,"utf-8"));System.out.println(source+"[0,20](gbk): "+cutString(source,0,20,"gbk"));System.out.println(source+"[0,20](utf-8): "+cutString(source,0,20,"utf-8"));}?打印结果：
?写道我是abc[0,4](gbk): 我是