JAVA笔试题--Java选择题100道(7)

StudentCourse.hbm.xml

struts-config.xml

type=\

type=\ name=\ input=\

path=\

path=\

4．Java编程,打印昨天的当前时刻 public class YesterdayCurrent{ public void main(String[] args){ Calendar cal = Calendar.getInstance(); cal.add(Calendar.DATE, -1); System.out.println(cal.getTime()); } }

5.文件读写,实现一个计数器 public int getNum(){ int i = -1; try{

String stri=\

BufferedReader in = new BufferedReader(new FileReader(f)); while((stri=in.readLine())!=null){ i = Integer.parseInt(stri.trim()); }

in.close();

}catch(Exception e){ e.printStackTrace(); } return i; }

public void setNum(){ int i = getNum(); i++; try{

PrintWriter out=new PrintWriter(new BufferedWriter(new FileWriter(f,false)));

out.write(String.valueOf(i)); //可能是编码的原因，如果直接写入int的话，将出现java编码和windows编码的混乱，因此此处写入的是String

out.close() ; }catch(Exception e){ e.printStackTrace(); } }

6. 指出下面程序的运行结果: class A{ static{

System.out.print(\ }

public A(){

System.out.print(\ } }

class B extends A{ static{

System.out.print(\ }

public B(){

System.out.print(\ } }

public class Hello{

public static void main(String[] ars){ A ab = new B(); //执行到此处,结果: 1a2b ab = new B(); //执行到此处,结果: 1a2bab } }

注:类的static 代码段,可以看作是类首次加载(被虚拟机加载)执行的代码,而对于类的加载,首先要执行其基类的构造,再执行其本身的构造

7.写一个Singleton模式的例子 public class Singleton{

private static Singleton single = new Singleton(); private Singleton(){}

public Singleton getInstance(){ return single; } }

8 删除表的重复记录

如果记录完全相同才算重复记录,那么: (sql server2000下测试通过) select distinct * into #tmpp from tid delete from tid

insert into tid select * from #tmpp drop table #tmpp

如果有id主键(数字,自增1的那种),那么:(sql server2000下测试通过) delete from tableA where id not in

(select id = min(id) from tableA group by name

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