????27???е?????????κγ?????????cloneable??????????????????????????????????????????

??????????е?????????????漰?????????????????????

??????????????????ó????????????????????????ò??????????????????????????е??????????

????????super.clone()??????????????????????object?е?clone()????????????????????????????????????????ж????????????????????????????????洢????С?

????28??Integer??

????valueOf(String s) //??s??????????????????

????parseInt(String s) //??s????????int?????????

??????????????????????????????????

????29??java?У????class????????????Class?????????????????д????????????????????.class????У?????????Class?????????????????????????

???????class?????????????

????a????????????getClass()?????????????class???;

????b?????class?????????forName()????????????????class???

????c??????.class?????????class?????????????????????????????????.type???????????????????????class??????磺

 

???????????Σ?
Point pt = new Point(); 
????Class c1 = pt.getClass(); 
????System.out.println(c1.getName()); 
????try{ 
????Class c2 = Class.forName("Point"); 
????System.out.println(c2.getName()); 
????} 
????catch{……} 
????Class c3 = Point.class; 
????System.out.println(c3.getName()); 
????Class c4 = int.class; 
????System.out.println(c4.getName()); 
????Class c5 = Integer.TYPE; 
????System.out.println(c5.getName());

 

????

        30??java?е????api??????????????????????????????????????????????????????????????????????????д??Σ????á?

????31??runtime???????????ó????????????????????jvm???????棬????е???檔??getRuntime()??????????????

 

Runtime rt = Runtime.getRuntime();
System.out.println(rt.freeMemory());
System.out.println(rt.totalMemory());

 

???? ?????????????????????process. ???ó??????????

 

try{rt.exec("notepad");}
try{rt.exec(javac ArrayTest.java);};