• commons-lang包的StringUtils.split()和jdk自带split()的区别


    StringUtils的split()方法只能以单个字符进行切分,即使在使用StringUtils.split(String str, String splitChars),splitChars传入多个字符的字符串,也只会以splitChars中的所有包含的单个字符进行切分,具体如下:

    import org.apache.commons.lang.StringUtils;
    
    public class Test {
        public static void main(String[] args) {
            
            String s = "0012001230010023001230023";
            long time1 = System.currentTimeMillis();
            
            String[] split1 = s.split("123");
            
            long time2 = System.currentTimeMillis();
            
            String[] split2 = StringUtils.split(s, "123");
            
            long time3 = System.currentTimeMillis();
            
            System.out.println("用时1>>>."+(time2-time1));
            System.out.println("用时2>>>."+(time3-time2));
            
            for(int i=0,len=split1.length; i<len; i++){
                
                System.out.print(split1[i]);
                System.out.print("-");
            }
            
            System.out.println("");
    
            for(int i=0,len=split2.length; i<len; i++){
                
                System.out.print(split2[i]);
                System.out.print("-");
                
            }
        }
        
        
    }

    运行结果:

      用时1>>>.2
      用时2>>>.17
      001200-001002300-0023-
      00-00-00-00-00-00-

     另: StringUtils.split()是空指针安全的.

    附StringUtils.split(String str, String separatorChars, int max)的实现源码:

         private static String[] splitWorker(String str, String separatorChars, int max, boolean preserveAllTokens) {
                // Performance tuned for 2.0 (JDK1.4)
                // Direct code is quicker than StringTokenizer.
                // Also, StringTokenizer uses isSpace() not isWhitespace()
    
                if (str == null) {
                    return null;
                }
                int len = str.length();
                if (len == 0) {
                    return ArrayUtils.EMPTY_STRING_ARRAY;
                }
                List list = new ArrayList();
                int sizePlus1 = 1;
                int i = 0, start = 0;
                boolean match = false;
                boolean lastMatch = false;
                if (separatorChars == null) {
                    // 使用StringUtils.split(String str)时默认进入这个判断,使用空字符进行切割
                    while (i < len) {
                        if (Character.isWhitespace(str.charAt(i))) {
                            if (match || preserveAllTokens) {//遇到空字符进入此判断    ①
                                lastMatch = true;
                                if (sizePlus1++ == max) {
                                    i = len;
                                    lastMatch = false;
                                }
                                list.add(str.substring(start, i));//将截取的字符串放入list
                                match = false;
                            }
                            start = ++i;//将下一个字符作为截取开始点
                            continue;
                        }
                        lastMatch = false;
                        match = true;//如果不是separatorChars则置为true,以便下一个字符进入判断 ①
                        i++;
                    }
                } else if (separatorChars.length() == 1) {
                    // 截取字符是单个字符的情况   与默认空字符判断情况相同
                    char sep = separatorChars.charAt(0);
                    while (i < len) {
                        if (str.charAt(i) == sep) {
                            if (match || preserveAllTokens) {
                                lastMatch = true;
                                if (sizePlus1++ == max) {
                                    i = len;
                                    lastMatch = false;
                                }
                                list.add(str.substring(start, i));
                                match = false;
                            }
                            start = ++i;
                            continue;
                        }
                        lastMatch = false;
                        match = true;
                        i++;
                    }
                } else {
                    // standard case
                    while (i < len) {
                        if (separatorChars.indexOf(str.charAt(i)) >= 0) {//如果被切割字符串的第i个字符在separatorChars中,则切掉  (正是此处与jdk的split不同)
                            if (match || preserveAllTokens) {
                                lastMatch = true;
                                if (sizePlus1++ == max) {
                                    i = len;
                                    lastMatch = false;
                                }
                                list.add(str.substring(start, i));
                                match = false;
                            }
                            start = ++i;
                            continue;
                        }
                        lastMatch = false;
                        match = true;
                        i++;
                    }
                }
                if (match || (preserveAllTokens && lastMatch)) {
                    list.add(str.substring(start, i));
                }
                return (String[]) list.toArray(new String[list.size()]);
            }
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  • 原文地址:https://www.cnblogs.com/mr-level/p/5546268.html
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