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(2008-9-27 bbh)
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ͬÑùµÄÎÊÌâ¶¼ÊDz»Í¬µÄ˵·¨,ÎÒºÜÃÔºý,»¨ÁËÒ»ÍíÉ϶ÁÁËJava Virtual Machine SpecificationºÍ
The Java Language SpecificationµÄһЩÕ½Ú,×öÁ˺ܶàÊÔÑé,×ܽáÁËһϹØÓÚStringµÄÄÚÈÝ,»¹
ÓкܶàÄÚÈÝÎÒÒ²²»È·¶¨,ÔÚÏÂÃæÒ²¶¼Ìá³öÀ´ÁË,Ï£Íû¸ßÊÖÄÜÖ¸Õý.
Constant Pool³£Á¿³ØµÄ¸ÅÄî:
ÔÚ½²µ½StringµÄÒ»Ð©ÌØÊâÇé¿öʱ,×Ü»áÌáµ½String Pool»òÕßConstant Pool,µ«ÊÇÎÒÏëºÜ¶àÈ˶¼²»Ì«
Ã÷°×Constant Poolµ½µ×ÊǸöÔõôÑùµÄ¶«Î÷,ÔËÐеÄʱºò´æ´¢ÔÚÄÄÀï,ËùÒÔÔÚÕâÀïÏÈ˵һÏÂConstant PoolµÄÄÚÈÝ.
String PoolÊǶÔÓ¦ÓÚÔÚConstant PoolÖд洢String³£Á¿µÄÇøÓò.ϰ¹ß³ÆÎªString Pool,Ò²ÓÐÈ˳ÆÎª
String Constant Pool.ºÃÏñûÓÐÕýʽµÄÃüÃû??
ÔÚjava±àÒëºÃµÄclassÎļþÖÐ,ÓиöÇøÓò³ÆÎªConstant Pool,ËûÊÇÒ»¸öÓÉÊý×é×é³ÉµÄ±í,ÀàÐÍ
Ϊcp_info constant_pool[],ÓÃÀ´´æ´¢³ÌÐòÖÐʹÓõĸ÷ÖÖ³£Á¿,°üÀ¨Class/String/IntegerµÈ¸÷
ÖÖ»ù±¾JavaÊý¾ÝÀàÐÍ,ÏêÇé²Î¼ûThe Java Virtual Machine Specification 4.4Õ½Ú.
¶ÔÓÚConstant Pool,±íµÄ»ù±¾Í¨ÓýṹΪ:
cp_info {
u1 tag;
u1 info[];
}
tagÊÇÒ»¸öÊý×Ö,ÓÃÀ´±íʾ´æ´¢µÄ³£Á¿µÄÀàÐÍ,ÀýÈç8±íʾStringÀàÐÍ,5±íʾLongÀàÐÍ,info[]¸ù¾Ý
ÀàÐÍÂëtagµÄ²»Í¬»á·¢ÉúÏàÓ¦±ä»¯.
¶ÔÓÚStringÀàÐÍ,±íµÄ½á¹¹Îª:
CONSTANT_String_info {
u1 tag;
u2 string_index;
}
tag¹Ì¶¨Îª8,string_indexÊÇ×Ö·û´®ÄÚÈÝÐÅÏ¢,ÀàÐÍΪ:
CONSTANT_Utf8_info {
u1 tag;
u2 length;
u1 bytes[length];
}
tag¹Ì¶¨Îª1,lengthΪ×Ö·û´®µÄ³¤¶È,bytes[length]Ϊ×Ö·û´®µÄÄÚÈÝ.
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ΪÁËÏêϸÀí½âConstant PoolµÄ½á¹¹,ÎÒÃDzο´Ò»Ð©´úÂë:
String s1 = "sss111";
String s2 = "sss222";
System.out.println(s1 + " " + s2);
ÓÉÓÚ"sss111"ºÍ"sss222"¶¼Ê
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Cookie[] cookies = request.getCookies();
if(cookies!=null){
for(Cookie cookie : cookies){
if(cookie.getName().equals("mid")){
String mid = cookie.getValue();
}
}
}
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String mid ......
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Calendar time=Calendar.getInstance();
time.clear();
time.set(Calendar.YEAR,year); //year Ϊ int
time.set(Calendar.MONTH,i-1);//×¢Òâ,Calendar¶ÔÏóĬÈÏÒ»ÔÂΪ0
int day=time.getActualMaximum(Calendar.DAY_OF_MON ......