每日日报

今日问题

1、问题：导入的新工程，名字上出现感叹号。

      原因：工程的jar包libraries需要重新加载。

      解决：工程右键--》properties--》Java Build Path--》Libraries，remove以前的jar包，点选“Add JRES”，从工程中的web_root--》lib文件夹中选择jar包，并导入即可。

 

2、问题：java中的三元运算符"?"用法。

      例子： 

       String message=message==null?   "异常："+rootCause.getClass().getName():message;

       释疑：

        如果message==null为真，则赋值 "异常："+rootCause.getClass().getName()给message，否则把“错误信息message”赋值给message。

 

package homework;

import java.util.*;

import java.util.Scanner;

import javax.script.*;

import java.io.File; 

import java.io.InputStreamReader; 

import java.io.BufferedReader; 

import java.io.BufferedWriter; 

import java.io.FileInputStream; 

import java.io.FileWriter; 

import java.io.IOException;

import java.io.*;

public class math

{

    private static int n,min,max,c,cc,kh=0,xz,zts=0,zcts=0;//题目数，数值范围（最小及最大），操作数个数，乘除，括号，选择菜单，总题数，总错题数

    private static char[] d={'+','-','*','/'};//运算符

    private static Scanner sc=new Scanner(System.in);

    public static void main(String args[]){DZ();}//菜单

    public static void DZ()//菜单

    {

        System.out.println("请选择：");

        System.out.println(" 1.小学二年级口算题");

        System.out.println(" 2.小学三年级口算题");

        System.out.println(" 3.小学四年级口算题");

        System.out.println(" 4.错题本");

        xz=sc.nextInt();

        if(xz==4) {CTB();}//错题本

        else

        {

            System.out.println( "请输入题目总数：" );

           n=sc.nextInt();

           System.out.println("请输入数值的范围.");

           min=sc.nextInt();

           max=sc.nextInt();

           switch(xz)

           {

           case 1:

               while(max>100)

               {

                   System.out.println("小学二年级操作数范围不超过100，请重新输入最大值：");

                   max=sc.nextInt();

               }

               c=1;

               break;

           case 2:

               while(max>1000)

               {

                   System.out.println("小学三年级操作数范围不超过1000，请重新输入最大值：");

                   max=sc.nextInt();

               }

               System.out.println( "输入操作数个数：" );

               c=sc.nextInt()-1;

               while(c>3)

               {

                   System.out.println("小学三年级操作数不超过4个，请重新输入操作数个数：");

                   c=sc.nextInt()-1;

               }

               break;

           case 3:

               System.out.println( "输入操作数个数：" );

               c=sc.nextInt()-1;

               while(c>4)

               {

                   System.out.println("小学四年级操作数不超过5个，请重新输入操作数个数：");

                   c=sc.nextInt()-1;

               }

               System.out.println( "是否有括号？是请输入1,否请输入0：" );

               kh=sc.nextInt();

               break;

           }

           System.out.println( "是否有乘除法？是请输入1,否请输入0：" );

           cc=sc.nextInt();

           TM();//题目

        }

    }

    public static String Tm()//每题

    {

        Random r=new Random();

        int sz;

        String ch=null;

        double a=r.nextInt(max)+min;

        while(a>max){a=r.nextInt(max)+min;}

        if(xz==1)

        {

            int b;

            if(cc==0) {sz=r.nextInt(2);}

            else{sz=r.nextInt(4);}//乘除法

            b=r.nextInt(max)+min;

            while(b>max){b=r.nextInt(max)+min;}

            if(d[sz]=='/')

            {

                if(b==0){while(b==0||b>max) {b=r.nextInt(max)+min;}}//防止0为被除数

                if(a%b!=0)

                {

                    while(a%b!=0||a>max||b>max)

                    {

                        a=r.nextInt(max)+min;

                        b=r.nextInt(max)+min;

                    }

                }

            }

            if(d[sz]=='-'&&b>a){while(b>a||b>max) {b=r.nextInt(max)+min;}}

            ch=String.valueOf(a);

            ch+=String.valueOf(d[sz]);

            ch+=String.valueOf(b);

        }

        else

        {

            double[] b=new double[c];//操作数个数及数值范围

            int k=-1,h=-1,z;//左括号，右括号

            if(kh==1)//括号

            {

                z=r.nextInt(2);

                if(z==1)//随机增加括号

                {

                    k=r.nextInt(c-1);

                    if(k==0)//括号由开头起

                    {

                        ch=String.valueOf('(');

                        ch+=String.valueOf(a);

                        h=r.nextInt(c-1)+k+1;

                        while(h>c){h=r.nextInt(c-1)+k+1;}

                    }

                    if(k>0)//括号在式中

                    {

                        ch=String.valueOf(a);

                        h=r.nextInt(c)+k+1;

                        while(h>c){h=r.nextInt(c)+k+1;}

                    }

                }

                else{ch=String.valueOf(a);}

            }

            else{ch=String.valueOf(a);}

            for(int i=0;i<c;i++)

            {

                if(cc==0) {sz=r.nextInt(2);}

                else {sz=r.nextInt(4);}//乘除法

                ch+=String.valueOf(d[sz]);

                if(k>0&&i==k-1){ch+=String.valueOf('(');}

                b[i]=r.nextInt(max)+min;

                while(b[i]>max){b[i]=r.nextInt(max)+min;}

                if(d[sz]=='/'&&b[i]==0){while(b[i]==0||b[i]>max) {b[i]=r.nextInt(max)+min;}}//防止0为被除数

                ch+=String.valueOf(b[i]);

                if(i==h-1){ch+=String.valueOf(')');}//补“）”

            }

        }

        return ch;//以字符串形式定义算式

    }

    public static void TM()//总题

    {

        zts+=n;

        int j=0;

        String[] s=new String[n];

        while(j<n)//制作题目

        {

            s[j]=Tm();

            if(PC(j,s)==0)//是否重复

            {

                System.out.println((j+1)+"、"+s[j]+"=");

                j++;   

            }

        }

        ScriptEngine se=new ScriptEngineManager().getEngineByName("JavaScript");

        double[] sum=new double[n];

        for(int i=0;i<n;i++)

        {

            try{sum[i]=(Double)se.eval(s[i]);}

            catch(ScriptException e){e.printStackTrace();}

        }//字符串转算式计算结果

        DT(s,sum);//答题

    }

    public static int PC(int j,String[] s)//判重

    {

        for(int i=0;i<j;i++){if(s[i].equals(s[j])) {return 1;}}

        return 0;

    }

    public static void DT(String[] s,double[] sum)//答题

    {

        int mint,yd=0,w=0,yn=0;//时间，已答题目，错题数，yes or no

        double[] da=new double[n];//回答

        int[] cwcs=new int[n];

        double[] Da=new double[n];

        double[] Sum=new double[n];

        String[] Cw=new String[n];//错误题号

        System.out.println( "请设置答题时间（分钟）");

        mint=sc.nextInt();

        System.out.println( "开始答题 ！");

        long startTime=System.currentTimeMillis();

        while((System.currentTimeMillis()-startTime)/1000<=mint*60)

        {

            da[yd]=sc.nextDouble();

            yd++;

            if(yd==n){break;}

        }

        if(yd!=n){System.out.println( "时间到！答题结束！");}

        for(int i=0;i<n;i++)

        {

            if(da[i]!=sum[i])//判断答题对错

            {

                Cw[w]=s[i];

                Da[w]=da[i];

                Sum[w]=sum[i];

                cwcs[w]=1;

                w++;

                zcts++;

            }

        }

        try

        {

            File f=new File("CTB.txt");

            try(FileWriter writer = new FileWriter(f,true);BufferedWriter out = new BufferedWriter(writer);)

            {

                for(int i=0;i<w;i++){out.write(Cw[i]+"="+Sum[i]+",共做错了"+cwcs[i]+"次。\r\n");}

                out.flush();

                out.close();

            }

        }catch (IOException e) {e.printStackTrace();}

        double cw=(double)(n-w)*100/n;//正确率

        System.out.println( "你的正确率为 ：" +cw+"%");

        System.out.println( "你的错题如下 ：");//错题

        for(int i=0;i<w;i++){System.out.println((i+1)+"、"+Cw[i]+"="+Da[i]+" X"+" 正确答案:"+Sum[i]);}

        do

        {

            System.out.println("请选择：");

            System.out.println(" 1.再做一套题");

            System.out.println(" 2.错题重练");

            System.out.println(" 3.退出");

            yn=sc.nextInt();

            switch(yn)

            {

            case 1:

                TM();

                break;

            case 2:

                for(int i=0;i<w;i++)

                {

                    System.out.println((i+1)+"、"+Cw[i]+"=");

                    da[i]=sc.nextDouble();

                    if(da[i]!=Sum[i])

                    {

                        cwcs[i]++;

                        System.out.println((i+1)+"、X 正确答案为："+Sum[i]);

                        try

                        {

                            File f=new File("CTB.txt");

                            BufferedReader in=new BufferedReader(new FileReader(f));

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

                            String line;

                            while ((line = in.readLine()) != null)

                            {

                                String[] tokens = line.split(",");

                                if(tokens[0].equals(Cw[i]+"="+Sum[i]))

                                {

                                    out.println(line.replace(tokens[1], "共做错了"+cwcs[i]+"次。"));

                                }

                            }

                            in.close();

                            out.close();

                         }catch (IOException e) {e.printStackTrace();}

                    }

                }

                break;

            case 3:

                System.out.println( "你今天的正确率为 ：" +(zts-zcts)*100/zts+"%"+"\r\n");

                CTB();

                break;

            }          

        }while(yn!=3);

    }

    public static void CTB()//错题本

    {

        System.out.println("         错题本          ");

        try

        {

            File f=new File("CTB.txt");

            InputStreamReader reader = new InputStreamReader(new FileInputStream(f));

            BufferedReader br = new BufferedReader(reader);

            String line; 

            while ((line = br.readLine()) != null){System.out.println(line);}

            br.close();

        }catch (IOException e) {e.printStackTrace();}

    }

}