Please refer to following code which is related for mathematical tables practice. For all multiplication of numbers other than 15 * 9 it works properly but there is problem with 15 * 9 .
package com.test;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.Scanner;
public class Entry {
static Scanner scanIn;
static Random random;
static List<String> list;
static List<String> mistakeList;
static File mistakeFile;
static {
scanIn = new Scanner(System.in);
random = new Random();
list = new ArrayList<String>();
}
/**
* Main function to call the private methods.
*/
public static void main(String[] args) throws IOException {
mistakeFile = new File(args[0]);
if(!mistakeFile.exists())
{
try {
mistakeFile.createNewFile() ;
} catch (IOException e) {
e.printStackTrace();
}
}
mistakeList = getFileContent(mistakeFile);
System.out.println("Please enter max limit .....");
Integer maxLimit = Integer.parseInt(scanIn.nextLine());
System.out.println("Please enter min limit .....");
Integer minLimit = Integer.parseInt(scanIn.nextLine());
System.out.println("Enter the number if iterations ..... ");
Integer iterations = Integer.parseInt(scanIn.nextLine());
executeTable(maxLimit, minLimit, iterations);
scanIn.close();
writeIntoFile();
}
/**
*
* Multiplication logic which outputs two numbers, take input from user and
* matches it with result of multiplicaion.
*/
private static void executeTable(Integer maxLimit, Integer minLimit,
Integer iterations) {
int skipCount = 0;
for (int iTemp = 0; iTemp < iterations; iTemp++) {
try
{
Integer num1 = getNextRandomInt(minLimit, maxLimit);
Integer num2 = getNextRandomInt(2, 9);
if (list.contains(num1 + "_X_" + num2) && skipCount < 10) {
iTemp = iTemp - 1;
skipCount++;
continue;
}
skipCount = 0;
System.out.println(num1 + " X " + num2 + " = ");
Integer usrAnswer = Integer.parseInt(scanIn.nextLine());
Integer answer = num1 * num2;
if (usrAnswer != answer) {
System.out.println("WRONG!! The correct answer is " + num1
+ " X " + num2 + " = " + answer);
if(!mistakeList.contains(num1 + "_X_" + num2))
{
mistakeList.add(num1 + "_X_" + num2);
}
} else {
if(!list.contains(num1 + "_X_" + num2))
{
list.add(num1 + "_X_" + num2);
}
}
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
/**
* Gets next random number
*
*/
private static Integer getNextRandomInt(Integer minLimit, Integer maxLimit) {
Integer number = random.nextInt();
if(maxLimit < minLimit)
{
maxLimit = maxLimit + minLimit ;
minLimit = maxLimit - minLimit ;
maxLimit = maxLimit - minLimit ;
}
number = (number % (maxLimit - minLimit + 1));
if (number < 0) {
number = -number;
}
number += minLimit;
return number;
}
/**
* Records commom mistake in file
*/
private static void writeIntoFile() throws IOException
{
String fileContent = "" ;
for(String data : mistakeList)
{
fileContent = fileContent +data+ "\r\n" ;
}
try (FileWriter fw = new FileWriter(mistakeFile.getAbsoluteFile(), false);
BufferedWriter bw = new BufferedWriter(fw)) {
bw.write(fileContent);
bw.close();
}
}
/**
*Returns file content.
*
*/
private static List<String> getFileContent(File file) {
List<String> lst = new ArrayList<String>();
try (BufferedReader br = new BufferedReader(new FileReader(file))) {
String sCurrentLine;
while ((sCurrentLine = br.readLine()) != null) {
lst.add(sCurrentLine);
}
} catch (IOException e) {
e.printStackTrace();
}
return lst;
}
}
The console output is as follows .
Please enter max limit .....
15
Please enter min limit .....
15
Enter the number if iterations .....
100
15 X 2 =
30
15 X 8 =
120
15 X 9 =
135
WRONG!! The correct answer is 15 X 9 = 135
Though 135 proper input is provided the above program shows error for it. Dont know whats problem with 15 * 9
Adding more description.
The above program generates two random number within a limit and user has to enter the correct answer for it.Example.The above program displays two numbers like "15 X 8 =" and user has to enter 120. The above program works well for all other combinations other than "15 X 9 =". User enters 135 which is correct answer still the program shows it incorrect answer.
