java 考试小程序

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2-2

public class ex2_2

{ public static void main (String[] args)

{System.out.println(“Welcome to Java World!”);

}

2-3

import java.awt.Applet;

import java.awt.Graphics;

public class ex2_3 extends Applet

{public void paint(Graphics g)

{g.drawString(“Welcome to Java Applet World”,10,20);

}

2-4

<html>

<body>

</applet>

</body>

</html>

3-8

(1)2 (2)3 (3)false (4)8

3-9

（一）

import java.io.*;

public class ex3_9

{ public static void main (String[] args)

{ float x=0f,y=0f;int z=0;

String s;

try

{System.out.print("请输入一个浮点数：");

BufferedReader a=new BufferedReader(new InputStreamReader(System.in));

s=a.readLine();

x=Float.parseFloat(s);

z=(long)x;

y=x-z;

}catch(IOException e){}

System.out.println("整数部分是："+z);

System.out.println("小数部分是："+y);

}

（二）

import java.io.*;

public class ex3_9

{

public static void main(String args[])

{String s;

double d;

int i;boolean b=false;

do{

try{

System.out.println("请输入一个浮点数:");

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

s=br.readLine();

i=s.indexOf('.');

//System.out.println("position of . is:"+i);

d=Double.parseDouble(s);

System.out.println(d+"整数部分为:"+(long)d);

if(i==-1)

System.out.println(d+"小数部分为:"+0.0);

else

System.out.println(d+"小数部分为:"

+Double.parseDouble(((s.charAt(0)=='-')?"-":"")+"0."+s.substring(i+1,s.length())));

System.out.println(s.length());

b=false;

}

catch(NumberFormatException nfe)

{System.out.println("输入浮点数格式有误!");

b=true;

}

catch(IOException ioe)

{b=false;}

}while(b);

}}

3-10:

import java.io.*;

public class ex3_10

{ public static void main (String[] args)

{ int i,j, max=0,min=0;

String s;

try

{System.out.print("请输入十个整型数：");

BufferedReader a=new BufferedReader(new InputStreamReader(System.in));

s=a.readLine();

i=Integer.parseInt(s);

max=min=i;

for(j=0;j<9;j++)

{BufferedReader b=new BufferedReader(new InputStreamReader(System.in));

s=b.readLine();

i=Integer.parseInt(s);

if(max<i)

max=i;

if(min>i)

min=i;

}

}catch(IOException e){}

System.out.println("十个数字中最大的数是："+max);

System.out.println("十个数字中最小的数是："+min);

}

4-7

class Student

{

String stuId;

String classId;

String stuName;

char stuSex;

int stuAge;

Student(String a,String b,String c,char d,int e)

{ stuId=a;

classId=b;

stuName=c;

stuSex=d;

stuAge=e;

}

String getStuId()

{return stuId;

}

String getClassId()

{return classId;

}

int getStuAge()

{return stuAge;

}

boolean setStuAge(int newAge)

{if(newAge>0&&newAge<130)

{stuAge=newAge;

return true;

}

else

{System.out.println(“非法学生年龄！”);

return false；

}

4-8

public class ex4_8

{public static void main(String args[])

{ Student demoStudent=new Student( );

}

4-10

答：构造方法是一种特殊的方法，每个类都可以有一个或多个构造方法。在程序创建某类的对象时系统会自动调用执行该类的构造方法，构造方法中定义了对新建对象的初始化操作。构造方法的方法名与它所在的类名相同，它没有返回类型，一般不能由编程人员显式地直接调用。

题目中有两处错误，构造方法没有返回类型，也不需要返回操作。修改后的程序如下：

Student(int sno,String sname)

{ studentNo=sno;

studentName=sname;

}

6-4

(一)public class ex6_4

{public static void main(String args[])

{final int NUMBER=100;

int count=10;

int randomNum=0;

int probability[]=new int[6];

for(int i=0;i<NUMBER;i++)

{randomNum=(int)(Math.random()*6)+1;

probability[randomNum-1]++;}

for(int i=0;i<6;i++)

{ System.out.println(“/n”+(i+1)+”:/t”+ (double)probability[i]/100);}

}

（二）

class MathRandom

{

public static void main(String args[])

{

int k=0,a=0,b=0,c=0,d=0,e=0,f=0;

double aa=0.0,bb=0.0,cc=0.0,dd=0.0,ee=0.0,ff=0.0;

System.out.println("以下是100个数:");

for(int i=0;i<100;i++)

{

k=(int)(Math.random()*6)+1;

switch(k)

{

case 1:a++;break;

case 2:b++;break;

case 3:c++;break;

case 4:d++;break;

case 5:e++;break;

case 6:f++;break;

}

aa=(double)a/100;bb=(double)b/100; cc=(double)c/100;

dd=(double)d/100; ee=(double)e/100; ff=(double)f/100;

System.out.println("1出现的次数是"+a+"概率是:"+aa);

System.out.println("1出现的次数是"+b+"概率是:"+bb);

System.out.println("1出现的次数是"+c+"概率是:"+cc);

System.out.println("1出现的次数是"+d+"概率是:"+dd);

System.out.println("1出现的次数是"+e+"概率是:"+ee);

System.out.println("1出现的次数是"+f+"概率是:"+ff);

System.out.println("以下是1000个数:");

a=0;b=0;c=0;d=0;e=0;f=0;

for(int i=0;i<1000;i++)

{

k=(int)(Math.random()*6)+1;

switch(k)

{

case 1:a++;break;

case 2:b++;break;

case 3:c++;break;

case 4:d++;break;

case 5:e++;break;

case 6:f++;break;

}

aa=(double)a/1000;bb=(double)b/1000; cc=(double)c/1000;

dd=(double)d/1000; ee=(double)e/1000; ff=(double)f/1000;

System.out.println("1出现的次数是"+a+"概率是:"+aa);

System.out.println("1出现的次数是"+b+"概率是:"+bb);

System.out.println("1出现的次数是"+c+"概率是:"+cc);

System.out.println("1出现的次数是"+d+"概率是:"+dd);

System.out.println("1出现的次数是"+e+"概率是:"+ee);

System.out.println("1出现的次数是"+f+"概率是:"+ff);

} }

6-11

import java.io.*;

public class ex6_11

{ public static void main (String[] args)

{ int a[]=new int[10];

int max=0,min=0,sum=0;

double average=0.0;

String s;

try

{System.out.print("请输入十个整型数：");

BufferedReader aa=new BufferedReader(new InputStreamReader(System.in));

s=aa.readLine();

a[0]=Integer.parseInt(s);

max=min=sum=a[0];

for(int i=1;i<=9;i++)

{BufferedReader bb=new BufferedReader(new InputStreamReader(System.in));

s=bb.readLine();

a[i]=Integer.parseInt(s);

sum=sum+a[i];

if(max<a[i])

max=a[i];

if(min>a[i])

min=a[i];

}

average=(double)sum/10;

}catch(IOException e){}

System.out.println("最大值是："+max);

System.out.println("最小值是："+min);

System.out.println("平均值是："+average);

System.out.println("所有元素的和是："+sum);

}

6-17

import java.io.*;

public class ex6_17

{ public static void main(String args[])

{ try

{ System.out.println("请输入一个字符串：");

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

String str = br.readLine();

if(isReversable(str))

System.out.println("这个字符串是回文。/n");

else

System.out.println("这个字符串不是回文。/n");

}catch(IOException e){}

}

public static boolean isReversable(String s)

{ for(int i=0,j=s.length()-1; i<j; i++,j--)

{ if(s.charAt(i) != s.charAt(j))

return false;

}

return true;

}

7-5

import java.applet.*;

import java.awt.*;

import java.awt.event.*;

public class ex7_5 extends Applet implements ActionListener

{String msg=”I love China!”;

Button btn1=new Button(“放大”);

Button btn2=new Button(“缩小”);

int fontsize;

public void init()

{add(btn1);

add(btn2);

fontsize=12;

btn1.addActionListener(this);

btn2.addActionListener(this);

}

public void paint(Graphics g)

{Font newFont,oldFont;

oldFont=g.getFont();

newFont=new Font(oldFont.getFontName(),oldFont.getStyle(),fontsize);

g.setFont(newFont);

g.drawString(msg,10,100);

}

public void actionPerformed(ActionEvent e)

{if (e.getSource()==btn1)

fontsize++;

else if(e.getSource()==btn2)

fontsize--;

repaint();

}