Question

My code is supposed to read input from a .txt file, and then do different things to sort it. The first int is the length. My main problem is I can not figure out why I keep getting a mismatch error, or if i put in ‘junk’ statements, the program never finishes. I’ll post the .txt first, and then the program.

15
Smith, John
26
Baker
Jones, Susan
15
Student
Mouse, Mickey
31
Theme park employee
Mouse, Mighty
48
Cartoon super hero
Anderson, William
35
Computer Programmer
Parker, Cindy
18
Author
McCain, John
20
Student
Armstrong, Michelle
17
Student
Thompson, Anne
29
Doctor
Li, Steve
15
Student
James, Tanya
20
Student
Moore, James
32
Teacher
Andrews, Julie
75
Actress
Obama, Michelle
46
Lawyer
Michaels, Todd
51
Student

//Don’t forget to copy the blank line at the end.

program starts here.

import java.util.Scanner;
import java.io.*;
public class SortAndDisplayCustomerData
{
public int length; //The length of the names, ages, and occupations arrays
public String[] names;
public int[] ages;
public String[] occupations;
public int count; //The length of the studentNames and studentAges arrays
public String[] studentNames;
public int[] studentAges;
public int i, minPos, Temp2, y, minVal;
public String Temp, Temp3, temp2, minVal2;

public void getDataFromFile()
{
Scanner keyboard = new Scanner(System.in);
    Scanner inputStream = null;
System.out.println("wtf");
    try
    {
        inputStream = new Scanner(new FileInputStream("NameAgeOcc.txt"));
    }

    catch(FileNotFoundException error)
    {
        System.out.println("Unable to open input file.");
        System.exit(0);
    }
    System.out.println("wtf2");
    length=inputStream.nextInt();
    //String junk = keyboard.nextLine();
    System.out.println("wtf3");
    names = new String[length];
    ages = new int[length];
    occupations = new String[length];
    for(i=0;i<length;i++)
    {
        names[i]=inputStream.nextLine();
        ages[i]=inputStream.nextInt();
        occupations[i]=inputStream.nextLine();
    }
    inputStream.close();
} 

public void displayAllFileData()
{
System.out.println("wtf3");
System.out.printf("%-25s%-8s%24s%n","Names","  Ages","  Occupations");
    for(i=0;i<length;i++)
    {
        System.out.printf("%-25s%6d%-24s%n",names[i],ages[i],occupations[i]);
    }
}
public void sortAllDataByAge()
{
    for(i=0;i<length;i++)
    {
        minVal=ages[i];
        minPos=i;
        for(y=i+1;y<length;y++)
        {
            if(ages[y]<minVal)
            {
                minVal=ages[y];
                minPos=y;
            }
        }
        Temp2 = ages[minPos];
        ages[minPos] = ages[i];
        ages[i] = Temp2;
        Temp = names[minPos];
        names[minPos] = names[i];
        names[i] = Temp;
        Temp3 = occupations[minPos];
        occupations[minPos] = occupations[i];
        occupations[i] = Temp3;
    }
}
public void extractStudentData()
{
    count=0;
    for (i=0;i<length;i++)
    {
        if(occupations[i].equalsIgnoreCase("student"))
        count++;
    }
    int j=0;
    studentAges = new int[count];
    studentNames = new String[count];
    for (i=0;i<length;i++)
    {
        if(occupations[i].equalsIgnoreCase("student"))
        {
            studentAges[j]=ages[i];
            studentNames[j]=names[i];
            j++;
        }
        }
}
public void displayStudentData()
{ 
System.out.printf("%n%-25s%-8s%n","Names","  Ages");

    for (i=0;i<count;i++)
    {
        System.out.printf("%-25s%6d%n",studentNames[i],studentAges[i]);
    }

}
public void sortStudentDataAlpha()
{ 
    for(i=0;i<count;i++)
    {
        minVal2=studentNames[i];
        minPos=i;
        for(y=i+1;y<count;y++)
        {
            if(studentNames[y].compareToIgnoreCase(minVal2)<0)
            {
                minVal2=studentNames[y];
                minPos=y;
            }
        }
        Temp = studentNames[minPos];
        studentNames[minPos] = studentNames[i];
        studentNames[i] = Temp;
        Temp2 = studentAges[minPos];
        studentAges[minPos] = studentAges[i];
        studentAges[i] = Temp2;
    }
}

}

Answer 1

Following a nextInt() you should eat up the line-break char, otherwise you’ll be expecting a String (for the names in your text file) and you’ll get an empty string (line break). Then you’ll have a nextInt() again but the pointer in the text file will be on the name (String).

For example, your program is following a path like this:

32 
Teacher 
Andrews, Julie 
75 
Actress 
Obama, Michelle 

nextInt() -> 32 nextLine() -> nextLine() -> Teacher
nextInt() -> Andrews, [Type Mismatch]