處理文本對 Java 應用來說應該算是家常便飯了，在 1.4 出現之前， Java 自身提供的 API 非常有限，如 String 、 StringTokenizer 、 StringBuffer ，操作也比較單一。無非就是查找 substring 、分解、合并等等。到 1.4 的出現可以說 Java 的文字處理上了一個臺階，因為它支持 regular expression 了。這可是個重量級而方便的東東啊，缺點是太復雜，學習起來有一定難度。相較而言， Jakarta Commons 提供的 StringUtils 和 WordUtils 至今還維持著那種簡潔而強大的美，使用起來也很順手。來看一個例子：

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package sean.study.jakarta.commons.lang;

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import org.apache.commons.lang.StringUtils;

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public class StringUtilsAndWordUtilsUsage {

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??? public static void main(String[] args) {

???????

??????? // data setup

??????? String str1 = "";

??????? String str2 = " ";

??????? String str3 = "\t";

??????? String str4 = null;

??????? String str5 = "123";

??????? String str6 = "ABCDEFG";

??????? String str7 = "It feels good to use Jakarta Commons.\r\n";

???????

??????? // check for empty strings

??????? System.out.println("==============================");

??????? System.out.println("Is str1 blank? " + StringUtils.isBlank(str1));

??????? System.out.println("Is str2 blank? " + StringUtils.isBlank(str2));

??????? System.out.println("Is str3 blank? " + StringUtils.isBlank(str3));

??????? System.out.println("Is str4 blank? " + StringUtils.isBlank(str4));

???????

??????? // check for numerics

??????? System.out.println("==============================");

??????? System.out.println("Is str5 numeric? " + StringUtils.isNumeric(str5));

??????? System.out.println("Is str6 numeric? " + StringUtils.isNumeric(str6));

???????

??????? // reverse strings / whole words

??????? System.out.println("==============================");

??????? System.out.println("str6: " + str6);

??????? System.out.println("str6 reversed: " + StringUtils.reverse(str6));

??????? System.out.println("str7: " + str7);

??????? String str8 = StringUtils.chomp(str7);

??????? str8 = StringUtils.reverseDelimited(str8, ' ');

??????? System.out.println("str7 reversed whole words : \r\n" + str8);

???????

??????? // build header (useful to print log messages that are easy to locate)

??????? System.out.println("==============================");

??????? System.out.println("print header:");

??????? String padding = StringUtils.repeat("=", 50);

??????? String msg = StringUtils.center(" Customised Header ", 50, "%");

??????? Object[] raw = new Object[]{padding, msg, padding};

??????? String header = StringUtils.join(raw, "\r\n");

??????? System.out.println(header);

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??? }

}

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輸出的結果如下：

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==============================

Is str1 blank? true

Is str2 blank? true

Is str3 blank? true

Is str4 blank? true

==============================

Is str5 numeric? true

Is str6 numeric? false

==============================

str6: ABCDEFG

str6 reversed: GFEDCBA

str7: It feels good to use Jakarta Commons.

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str7 reversed whole words :

Commons. Jakarta use to good feels It

==============================

print header:

==================================================

%%%%%%%%%%%%%%% Customised Header %%%%%%%%%%%%%%%%

==================================================

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從代碼中我們可以大致了解到這個 StringUtils 類簡單而強大的處理能力，從檢查空串（對 null 的情況處理很得體），到分割子串，到生成格式化的字符串，使用都很簡潔，也很直截了當。