判断字符串是否为空的有趣测试:-)
package com.dt5000.homework.action;/** * @author wangpj ISchoole com.dt5000.ischool.util 2012-11-19 StringUtil.java * TODO:抽取了org.apache.commons.lang.StringUtils工具类的部分代码 下载地址： * http://commons.apache.org/lang/download_lang.cgi */public class StringUtil {/** * <p> * Checks if a CharSequence is empty ("") or null. * </p> * * <pre> * StringUtils.isEmpty(null) = true * StringUtils.isEmpty("") = true * StringUtils.isEmpty(" ") = false * StringUtils.isEmpty("bob") = false * StringUtils.isEmpty(" bob ") = false * </pre> * * <p> * NOTE: This method changed in Lang version 2.0. It no longer trims the * CharSequence. That functionality is available in isBlank(). * </p> * * @param cs * the CharSequence to check, may be null * @return {@code true} if the CharSequence is empty or null * @since 3.0 Changed signature from isEmpty(String) to * isEmpty(CharSequence) */public static boolean isEmpty(CharSequence cs) {return cs == null || cs.length() == 0;}/** * <p> * Checks if a CharSequence is not empty ("") and not null. * </p> * * <pre> * StringUtils.isNotEmpty(null) = false * StringUtils.isNotEmpty("") = false * StringUtils.isNotEmpty(" ") = true * StringUtils.isNotEmpty("bob") = true * StringUtils.isNotEmpty(" bob ") = true * </pre> * * @param cs * the CharSequence to check, may be null * @return {@code true} if the CharSequence is not empty and not null * @since 3.0 Changed signature from isNotEmpty(String) to * isNotEmpty(CharSequence) */public static boolean isNotEmpty(CharSequence cs) {return !StringUtil.isEmpty(cs);}/** * <p> * Checks if a CharSequence is whitespace, empty ("") or null. * </p> * * <pre> * StringUtils.isBlank(null) = true * StringUtils.isBlank("") = true * StringUtils.isBlank(" ") = true * StringUtils.isBlank("bob") = false * StringUtils.isBlank(" bob ") = false * </pre> * * @param cs * the CharSequence to check, may be null * @return {@code true} if the CharSequence is null, empty or whitespace * @since 2.0 * @since 3.0 Changed signature from isBlank(String) to * isBlank(CharSequence) */public static boolean isBlank(CharSequence cs) {int strLen;if (cs == null || (strLen = cs.length()) == 0) {return true;}for (int i = 0; i < strLen; i++) {if (Character.isWhitespace(cs.charAt(i)) == false) {return false;}}return true;}/** * <p> * Checks if a CharSequence is not empty (""), not null and not whitespace * only. * </p> * * <pre> * StringUtils.isNotBlank(null) = false * StringUtils.isNotBlank("") = false * StringUtils.isNotBlank(" ") = false * StringUtils.isNotBlank("bob") = true * StringUtils.isNotBlank(" bob ") = true * </pre> * * @param cs * the CharSequence to check, may be null * @return {@code true} if the CharSequence is not empty and not null and * not whitespace * @since 2.0 * @since 3.0 Changed signature from isNotBlank(String) to * isNotBlank(CharSequence) */public static boolean isNotBlank(CharSequence cs) {return !StringUtil.isBlank(cs);}}