commons-lang包的StringUtils.split()和jdk自帶split()的區別

StringUtils的split()方法只能以單個字符進行切分,即使在使用StringUtils.split(String str, String splitChars),splitChars傳入多個字符的字符串,也只會以splitChars中的所有包含的單個字符進行切分,具體如下:

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("用時1>>>."+(time2-time1));
        System.out.println("用時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("-");
            
        }
    }
    
    
}

 

運行結果:

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

 另: StringUtils.split()是空指針安全的.

 

 

附StringUtils.split(String str, String separatorChars, int max)的實現源碼:

     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)時默認進入這個判斷,使用空字符進行切割
                while (i < len) {
                    if (Character.isWhitespace(str.charAt(i))) {
                        if (match || preserveAllTokens) {//遇到空字符進入此判斷    ①
                            lastMatch = true;
                            if (sizePlus1++ == max) {
                                i = len;
                                lastMatch = false;
                            }
                            list.add(str.substring(start, i));//將截取的字符串放入list
                            match = false;
                        }
                        start = ++i;//將下一個字符作為截取開始點
                        continue;
                    }
                    lastMatch = false;
                    match = true;//如果不是separatorChars則置為true,以便下一個字符進入判斷 ①
                    i++;
                }
            } else if (separatorChars.length() == 1) {
                // 截取字符是單個字符的情況   與默認空字符判斷情況相同
                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個字符在separatorChars中,則切掉  (正是此處與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()]);
        }