JAVA¶ÁÊé±Ê¼Ç£¨¶þ£©
²Ù×÷·û
1.λ²Ù×÷·û
(a) >>>ÓÒÒÆ£¬¸ßλÓÃ0Ìî³ä£»
int a = 14;
int b = 2;
System.out.println(a >>> b);// 3
int c = -14;
int d = 2;
System.out.println(c >>> d);// 1073741820
(b) >>·ûºÅλ²»±ä£¬ÆäËûλÓÒÒÆ£¬¸ßλÓÃ0Ìî³ä£¬Æä½á¹ûÓëa/2bÏàͬ£»
int a = 14;
int b = 2;
System.out.println(a >> b);// 3
int c = -14;
int d = 2;
System.out.println(c >> d);// -4
System.out.println(Math.floor(a / Math.pow(2, b))); // 3.0
System.out.println(Math.floor(c / Math.pow(2, d))); // -4.0
(c) <<·ûºÅλ²»±ä£¬ÆäËûλ×óÒÆ£¬µÍλÓÃ0Ìî³ä£¬Æä½á¹ûÓëa×2bÏàͬ£»
int a = 14;
int b = 2;
System.out.println(a << b);// 56
int c = -14;
int d = 2;
System.out.println(c << d);// -56
System.out.println(Math.floor(a * Math.pow(2, b))); // 56.0
System.out.println(Math.floor(c * Math.pow(2, d))); // -56,0
(d) ¶ÔÓÚjava.util.MathÖеÄceil¼°floorº¯Êý£¬Òª×¢Òâ²ÎÊýµÄÀàÐÍ
int a = 14;
int b = 3;
System.out.println(Math.floor(a / b)); // 4
System.out.println(Math.ceil(a / b)); // 4
double c = 14d;
double d = 3d;
System.out.println(Math.floor(c / d)); // 4
System.out.println(Math.ceil(c / d)); // 5
ÈçÉÏËùʾ£ºÓÉÓÚaºÍbÁ½¸ö²ÎÊý¶¼ÊÇintÀàÐ͵ģ¬Òò´ËÔÚÖ´ÐÐa/bºó£¬»á×öÒ»¸öÒþʽµÄÀàÐÍת»»£¬½«½á¹ûת³ÉintÀàÐ͵ģ¬ÕâÑù¾Í»á½«Ð¡ÊýλÉáÆú¡£Òò´ËÔÚÓõ½ceilºÍfloorº¯Êýʱ£¬Ó¦¸Ã×¢Òâ±í´ïʽ¼ÆËãºóËùÉú³ÉµÄ½á¹ûµÄÊý¾ÝÀàÐÍ¡£
Ïà¹ØÎĵµ£º
Ò»¡¢Java ClassLoader
1£¬Ê²Ã´ÊÇClassLoader
Óë C »ò C++ ±àдµÄ³ÌÐò²»Í¬£¬Java ³ÌÐò²¢²»ÊÇÒ»¸ö¿ÉÖ´ÐÐÎļþ£¬¶øÊÇÓÉÐí¶à¶ÀÁ¢µÄÀàÎļþ×é³É£¬Ã¿Ò»¸öÎļþ¶ÔÓ¦ÓÚÒ»¸ö Java Àà¡£
´ËÍ⣬ÕâЩÀàÎļþ²¢·ÇÁ¢¼´È«²¿¶¼×°ÈëÄڴ棬¶øÊǸù¾Ý³ÌÐòÐèҪװÈëÄÚ´æ¡£ClassLoader ÊÇ JVM Öн«Àà×°ÈëÄÚ´æµÄÄDz¿·Ö¡£
¶øÇÒ£¬Java ClassLoader ......
1.final¹Ø¼ü×ÖÐÞÊÎÀàʱ£¬ËµÃ÷ÆäÀ಻ÄÜÓÐ×ÓÀ࣬Ҳ¾ÍÊÇ˵¸ÃÀ಻Äܱ»¼Ì³Ð£¬¸ÃÀàµÄ³ÉÔ±±äÁ¿ÔÚÕâÀォ²»Æð×÷Óá£
2.final¹Ø¼ü×ÖÐÞÊη½·¨Ê±£¬ËµÃ÷¸Ã·½·¨²»Äܱ»ÖØд£¬ÒòΪÀ඼²»Äܱ»¼Ì³ÐÁË£¬·½·¨¾Í¸ü²»ÄÜÖØдÁË¡£
3.ÀàÀï¿ÉÒÔº¬ÓÐfinal¹Ø¼ü×ÖÐÞÊεķ½·¨¡£
4.ÔÚjavaÀ³éÏóÀà×îÉÙÒªº¬ÓÐÒ»¸ö³éÏó·½·¨£¬ÈÃËüµÄ×ÓÀàȥʵÏÖÕâ¸ö³éÏó·½· ......
×Ô¶¯×°ÏäºÍ×Ô¶¯²ðÏäÊÇjava5.0°æ±¾ÒýÈëµÄ£¬ÄÜ×Ô¶¯½«»ù±¾ÀàÐÍת»»Îª¶ÔÓ¦µÄ»ù±¾ÀàÐÍ°ü×°¶ÔÏó£¬ÄÇôÎÒÃDZȽÏÒ»ÏÂËûÃǵÄÐÔÄÜÇé¿ö¡£
package com.wmmad.test;
import junit.framework.TestCase;
/**
* @author madding.lip
*
* <pre>
* class: compare the autoboxing and unboxing and normal's performance
......
package homework01;
public class TestWhile {
public static double factorial(int n) //Çó½×³Ëº¯Êý
{
if(n==0) return 1;
else return n* factorial(n-1);
}
public static void main(String[] args) {
System.out.println(factorial(170));//test:ÄÜ´òÓ¡³öÀ´£ ......
Ò».´úÂëÓÅ»¯
¡¡¡¡ÄÚ´æ»áÒç³ö¿Ï¶¨ºÍ´úÂëÌÓ²»Á˹Øϵ,99.99%ѧjavaµÄÈ˶¼ÖªµÀÀ¬»ø»ØÊÕÆ÷ÊÇ javaµÄÒ»´óÓŵ㲢¾Ý´ËÀ´³°Ð¦C++¡£ÏÔÈ»Õâ¸öÌØÐÔΪ´úÂë±àдÕßÊ¡Á˲»ÉÙÊ£¬µ«Õâ¸öÌØÐÔÈ´´øÀ´Á˲»ÉÙÒþ»¼¡£¾Ù¸öÀý×ÓÔÚÓÎÏ·µ±Öо³£Óв»Í¬³¡¾°µÄÇл»£¬Èç´ÓÓÎÏ·Âß¼Í˵½Ö÷²Ëµ¥Âß¼,¶ÔÓÎÏ·Âß¼¶ÔÏóµÄ̬¶ ......