Trying to sort Array<int, String>

[ddc]

I'm new to the forum and am trying to sort a custom Class Object array in descending order. First, lexicographically based on the String. Second, numerically based on the integer. I am having trouble getting it to sort lexicographically and haven't gotten around to sorting it numerically yet because I am having problems getting the program to output properly. I believe the error lies around line 84. I also copied and pasted the code from the separate class file that holds the Player object and placed it below the main program code. Any help would be greatly appreciated!


import java.io.*;
import java.util.*;


public class ProjectFive
{
public static void main(String[] args) throws IOException
{
final int NUM_PLAYERS = 6;
String string1 = "Player", string2 = "Jersey Number";


//TODO Initialize array of objects
Player[] p = new Player[NUM_PLAYERS];


File file1 = new File("Team.txt");
Scanner inFile = new Scanner(file1);


//TODO Read data from file into array
for(int i = 0; i < p.length; i++)
{
p[i] = new Player(inFile.nextInt(), inFile.nextLine().trim());
}

inFile.close();

System.out.printf("%10s%20s\n", string1, string2);


//TODO List data in array (unsorted)
for(int i = 0; i < p.length; i++)
{
System.out.printf("%10s", p[i].getPlayerName());
System.out.printf("%20d\n", p[i].getPlayerNum());
}


//TODO Sort data alphabetically
int startScan, index, minIndex;
// minValue temporarily holds the smallest
// element in the array - needed for swap below
// minValue will always have the same type as
// each member of the array
String minValue;

// The first time through, look at the array starting at
// the beginning. Swap the smallest value with the
// starting value.
// Each time after that, look at the array starting at
// the next index, because you know that the smallest
// value(s) is/are already sorted at the beginning
// of the array.
for (startScan = 0; startScan < (p.length-1); startScan++)
{

// At the start, the minimum value is just
// the first value in the array.
minValue = p[startScan].getPlayerName();
// For now, the minIndex is the index that we're
// starting at.
minIndex = startScan;


for(index = startScan + 1; index < p.length; index++)
{
// Compare and find the smallest value
if (p[index].getPlayerName().compareTo(minValue) < 0)
{
// The array element with the minimum value
// is saved in the minValue variable
minValue = p[index].getPlayerName();
// Remember where the minimum value is
minIndex = index;
}
}
// Put the value from the front of the array
// into the place where the minimum value is
//p[minIndex] = new Player(p[startScan].getPlayerNum(), p[startScan].getPlayerName());
p[minIndex] = p[startScan];
// Put the minimum value at the front
// of the array
p[startScan] = new Player(p[minIndex].getPlayerNum(), minValue);
}

System.out.println();


System.out.printf("%10s%20s\n", string1, string2);


//TODO List data in array (now sorted alphabetically)
for(int i = 0; i < p.length; i++)
{
System.out.printf("%10s", p[i].getPlayerName());
System.out.printf("%20d\n", p[i].getPlayerNum());
}

//TODO Sort data numerically


//TODO List data in array (now sorted numerically)


}
}




public class Player
{
//Private data fields
private int playerNum;
private String playerName;

//Constructor. This is the only place to write to data fields
public Player(int a, String b)
{
playerNum = a;
playerName = b;
}

//Accessor for Player Number
public int getPlayerNum()
{
return playerNum;
}

//Accessor for Player Name
public String getPlayerName()
{
return playerName;
}
}

[Carl Bochek]

I have a project due tonight that is almost identical to this, i.e., sort an object of strings and ints both numerically and alphabetically.

I'll post the e-mail I sent my teacher:


I can't get my selectSort method to work properly. It seems as though
there's a problem with how the accessor methods are passing info to the
variables. FYI, "read the text file into array" and "print as is" are
working properly and selectSort does something, just not sorting so all
components are speaking with each other just not in the right way.



Here is the method:


public static void selectionSort(Book[] bookData)
{
int startScan, index, minIndex, minValue;

for (startScan = 0; startScan < (bookData.length-1); startScan++)
{
minValue = bookData[startScan].getYear();
minIndex = startScan;
for(index = startScan + 1; index < bookData.length; index++)
{
if (bookData[index].getYear() < minValue)
{
minValue = bookData[index].getYear();
minIndex = index;
}
}
bookData[minIndex] = bookData[startScan];
bookData[startScan].getYear() = minValue;
}

for(int i=0; i<bookData.length; i++)
System.out.println(bookData[i].getYear() + bookData[i].getTitle());







This line: bookData[startScan].getYear() = minValue;

Returns this error:

Project52.java:121: unexpected type
required: variable
found : value
bookData[startScan].getYear() = minValue;
^

This is obviously the problem. I understand the difference between a
variable and a value and that you tell a variable to be a value but not
the other way around. However, I'm not sure how to remedy this.



For reference here is the class:

public class Book
{
private int year;
private String title;

public Book (int y, String t)
{
year = y;
title = t;
}

public int getYear()
{
return year;
}

public String getTitle()
{
return title;
}
}






LET'S GET THIS SOLVED!!!!

[Carl Bochek]

I'm new as well. Hello everyone!!!!

:)

[pbrockway2]

Hi Carl,

You should really start your own thread for your own question. And use code tags: put [CODE] at the start of your code and [/CODE] at the end that way the formatting is preserved.

Project52.java:121: unexpected type
required: variable
found : value
bookData[startScan].getYear() = minValue;

Perhaps you mean

minValue = bookData[startScan].getYear();

-------------------------------

@ddc - sorry about the hijack. Perhaps you would get a better response if you asked a specific question. You say you have having trouble and problems, but you don't give a precise description of what the program does (its output) and what you expected or intended it would do.

[Carl Bochek]

Hi.

Sorry,

I posted my question on here as we have identical problems: selection sort of a class that has an int data field and string data field both numerically and alphabetically.

[Carl Bochek]

Methods that sort numerically and alphabetically with data strings and ints from an object. I think you'll be able to tell them apart. I hope this helps:

public static void selectionSort(Book[] bookData)
{

int startScan, index, minIndex;
Book minValue;

for (startScan = 0; startScan < (bookData.length-1); startScan++)
{

minValue = bookData[startScan];
minIndex = startScan;

for(index = startScan + 1; index < bookData.length; index++)
{
if (bookData[index].getYear() < minValue.getYear())
{
minValue = bookData[index];
minIndex = index;
}
}

bookData[minIndex] = bookData[startScan];
bookData[startScan] = minValue;
}

for(int i = 0; i < bookData.length; i++)
{
System.out.println(bookData[i].getYear() + bookData[i].getTitle());
}

}






public static void selectionSort2(Book[] bookData)
{

int startScan, index, minIndex;
Book minValue;

for (startScan = 0; startScan < (bookData.length-1); startScan++)
{

minValue = bookData[startScan];
minIndex = startScan;

for(index = startScan + 1; index < bookData.length; index++)
{

if (bookData[index].getTitle().compareTo(minValue.getTitle()) <0)
{
minValue = bookData[index];
minIndex = index;
}
}

bookData[minIndex] = bookData[startScan];
bookData[startScan] = minValue;
}

for(int i = 0; i < bookData.length; i++)
{
System.out.println(bookData[i].getYear() + bookData[i].getTitle());
}

}

[gcalvin]

@OP: Is this a class project working on sort implementations or are you allowed to use Arrays.sort()?

-Gary-

[gandrew]

Dear Sir: You have two problems in your sort section. This looks like a bubble sort. You need to have a temporary holder when you are swapping your array elements. Secondly, you don't need to create a new Player object. You are just re-arranging an existing built array of Player objects. This is why you are losing the Player's associated number. I've added two or three statements and cleared out the comments. It seems to work with this data. Good luck.
Contents of Team.txt
-----------------------------
19
Jose Bautista
11
Alex Gonzalez
2
Aaron Hill
18
Mike McCoy
6
John McDonald
35
Lyle Overbay
--------------
Sorted data...

Player Jersey Number
Aaron Hill 2
Alex Gonzalez 11
John McDonald 6
Jose Bautista 19
Lyle Overbay 35
Mike McCoy 18
--------------------------------------

System.out.println("Sorted data...");
Player tempPlayer; // Use this as a temp holder

for (startScan = 0; startScan < (p.length-1); startScan++)
{

minValue = p[startScan].getPlayerName();
minIndex = startScan;


for(index = startScan + 1; index < p.length; index++)
{
if (p[index].getPlayerName().compareTo(minValue) < 0)
{
minValue = p[index].getPlayerName();
minIndex = index;
}
}
tempPlayer = p[minIndex]; // You need to store this Player

p[minIndex] = p[startScan];

p[startScan] = tempPlayer; // Perform this swap
} // for

System.out.println();


System.out.printf("%10s%20s\n", string1, string2);