Java笔试题

public class throwExpTest {
/**
  * @param args
  */
public static void main(String[] args) {
  System.out.println(fun1(4));
  System.out.println(fun1(3));
  System.out.println(fun1(2));
  System.out.println(fun1(1));
  System.out.println(fun1(0));
  System.out.println(fun1(-1));
  System.out.println(fun1(-2));
  System.out.println(fun1(-3));
  System.out.println(fun1(-4));  
}
public static int fun1(int i)
{
  try{
   return ((Exp1)(fun0(i))).mul(5);
  }catch(Exp2 e){ return e.add(i);}
  catch(Exp3 e){return e.add(i); }
catch(Exception e){return -2;}
  //return -1;
}
public static Exception fun0(int i)throws Exception{
  Exception e[]={null,new Exp1(),new Exp2(),new Exp3()};
  if(i>0)throw e[i];
  else if(i<0){e[0]=e[-i];}
  return e[0];
}
}
class Exp1 extends Exception{
int add(int i){return i+2;}
int mul(int i){return i*2;}
}
class Exp2 extends Exp1{
int add(int i){return i+3;}
int mul(int i){return i*3;}
}
class Exp3 extends Exp1{
int add(int i){return i+4;}
int mul(int i){return i*4;}
}

2，package ss.ff.jun.j2se;
public class returnTest {
//float e=1.6;
public String funs(String s){
  System.out.print("Hello"+"  ");
  return s;
}
String fun2(){
  return funs("yyy");
}
public static void main(String args[]){
  returnTest a=new returnTest();
  String b=a.funs("World");
  System.out.println(b);
  
  System.out.println(a.funs("What"));
  
  System.out.println(a.fun2());
  //只要动用了方法，里面的动作就有效输出，而不仅是返回一个数据类型。
}
}

3，package ss.ff.jun.j2se;
public class switchTest {
/**
  * @param args
  */
  String fun(int i){
   switch(i){
    case 1:return "Wang";
    case 2:return "Liu";  
    case 3:return "Zhu";
    case 4:return "Li";
    default: return "Null";
   }
  //return null;
   //int char byte short ; only this four can be used in switch;
  }
public static void main(String[] args) {
  // TODO Auto-generated method stub
  switchTest s=new switchTest();
  System.out.println(s.fun(2));
  System.out.println(s.fun(1));
  System.out.println(s.fun(5));
}
}

4，package ss.ff.jun.j2se.error;
public class charAndString {
/**
  * @param args
  */
public static void main(String[] args) {
  // TODO Auto-generated method stub
  String s="ello";
  char a='H';
  a+=s;
  System.out.println(a);
}
}