Effective Java ѧϰ±Ê¼Ç(4)
Õâ¸öÔÔòºÜ¼òµ¥£¬¾ÍÊÇʹÓÃ˽Óй¹Ô캯Êý·ÀÖ¹À౻ʵÀý»¯¡£
ÓÐʱ£¬ÎÒÃÇ»áдһЩ¹¤¾ßÀ࣬Èçjava.lang.Math »òÊÇ java.util.Arrays, ÕâЩÀàÖж¼ÊǾ²Ì¬º¯Êý£¬ÔÚÉè¼ÆµÄʱºò£¬ÕâЩÀಢ²»ÊÇÓÃÀ´±»ÊµÀý»¯µÄ¡£Õâ¸öʱºò£¬¾ÍºÜÓбØÒª°Ñ¹¹Ô캯Êý˽Óл¯¡£
public class UtilityClass {
private UtilityClass() {
throw new AssertionError();
}
}
¸ü±£ÏÕµÄÊÇÔÚ¹¹Ô캯ÊýÖÐÅ׸öÒì³£¡£
µ±È»£¬ÕâÖÖ·½·¨µÄȱµã»¹ÊÇÓеģ¬¾ÍÊÇÕâ¸öÀ಻Äܱ»¼Ì³ÐÁË¡£
Ïà¹ØÎĵµ£º
package com.yzy;
import java.util.regex.*;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
Pattern p=Pattern.compile("^[a-z]+");
Matcher m=p.matcher("a233"); //true
//Matcher m=p.matcher("2233") ......
±¾ÎÄÌṩjava¶àÏ̷ֱ߳ð¶¨Ê±¶Áдͬһ¸öÎļþµÄÑùÀý£¬ÆäÖÐÁ½¸öỊ̈߳¬Ò»¸öÿ·ÖÖÓдÈ뵱ǰʱ¼äµ½Ö¸¶¨Îļþ£¬ÁíÒ»¸öÏ̶߳Á³öÿ·ÖÖÓÐÂдµÄÄÚÈÝ¡£
ʹÓüòµ¥µÄThread.sleep¼¼ÊõʵÏÖ¶¨Ê±
package test.thread;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
im ......
1. Òò×Ó
ÉϴνéÉÜÁË¡¶JAVAʵÏÖAES¼ÓÃÜ¡·£¬ÖмäÌáµ½½üЩÄêDESʹÓÃÔ½À´Ô½ÉÙ£¬ÔÒò¾ÍÔÚÓÚÆäʹÓÃ56λÃÜÔ¿£¬±È½ÏÈÝÒ×±»Æƽ⣬½üЩÄêÀ´Öð½¥±»AESÌæ´ú£¬AESÒѾ±ä³ÉÄ¿Ç°¶Ô³Æ¼ÓÃÜÖÐ×îÁ÷ÐÐËã·¨Ö®Ò»£»AES¿ÉÒÔʹÓÃ128¡¢192¡¢ºÍ256λÃÜÔ¿£¬²¢ÇÒÓÃ128λ·Ö×é¼ÓÃܺͽâÃÜÊý¾Ý¡£±¾Îľͼòµ¥½éÉÜÈçºÎͨ¹ ......
ͨ³£,ÓÐÒ»ÀàÎÊÌâµÄ²úÉú¶¼ÊÇÓÉÓÚûÓÐÖØÔØhashCodeÕâ¸ö·½·¨. µ±ÄãÖØÔØequalsºó,hashCode±ØÐëÖØÔØ,·ñÔòÔÚʹÓÃHashMap, HashSet, HashtableµÄʱºò,»á³ö´í.
¶ÔÓÚhashCodeÓм¸¸öÔÔò.
1. ²»¹Üʲôʱºòµ÷ÓÃhashCode,Èç¹ûͬһ¸ö¶ÔÏóÓëhashCodeÏà¹ØµÄ×Ö¶ÎûÓÐÐ޸ĵĻ°,Õâ¸ö·½·¨µÄ·µ»ØÖµ±ØÐëÏàͬ. µ«²»±ØºÍÁíÒ»¸öÓ¦ÓóÌÐòÖеÄÖµÏàµÈ ......
package com.yzy;
import java.util.regex.*;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
Pattern p=Pattern.compile("^[a-z]+");
Matcher m=p.matcher("a233"); //true
//Matcher m=p.matcher("2233") ......