Read from a text file, sort it, and write it again

Question

So our professor has assigned us with a program which reads a text file he has provided us with; it sorts it, and creates a new file with the sorted stuff. He wants us to call three methods from the main i.e. read, sort, and write

I have done some of the work, but i'm confused what arguments to provide for io.sort. And how do i convert that text thing into an array to provide an argument Here's my code:

public void read() {
    try {
        Scanner myLocal = new Scanner(new File("dictionary.txt"));
        while (myLocal.hasNextLine()) {
            System.out.println(myLocal.nextLine());
        }
    } catch (IOException e) {
        System.out.println(e);
    }
}

public void sort(String[] arr) {
    int n = arr.length;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n - 1; j++) {
            /* ERROR: When j == 0, j - 1 == -1, which is out of bounds */
            if (arr[j - 1].compareTo(arr[j]) > 0) { 
                swap(j, arr);
            }
        }
    }
}

public void swap(int j, String[] arr) {
    String temp = arr[j - 1];
    arr[j - 1] = arr[j];
    arr[j] = temp;
}

public void write() {
    try {
        PrintStream writer = new PrintStream(new File("sorted.txt"));
        for (int i = 0; i < 100; i++) {
            writer.println(i);
        }
        writer.close();
    } catch (IOException e) {
        System.out.println(e);
    }
}

first step - instead of printing out the contents of the input file, store it in an array — Scary Wombat
– Scary Wombat, Commented Apr 10, 2018 at 5:04
somehow I have a feeling that your professor wants you to solve this assignement instead of the stackoverflow community — tom
– tom, Commented Apr 10, 2018 at 11:31

Shahbaz Malik · Accepted Answer · 2018-04-10 05:23:56Z

1

Here is how i've changed my read() method:

public void read()
{
    String[] myArray = new String[1000];
    try {
        Scanner myLocal = new Scanner( new File("dictionary.txt"));  
        String a = myLocal.nextLine();
        while (myLocal.hasNextLine()){
            for (int i=0; i<myArray.length; i++){
                myArray[i] = a;
            }                   

        }
    }
    catch(IOException e){
        System.out.println(e);
    }
}

answered Apr 10, 2018 at 5:23

Shahbaz Malik

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3 Comments

Scary Wombat Over a year ago

Now, the problem with this is that the scope of myArray is limited to the read method. Either add a return type of String[] or move the declaration of myArray to a field

Scary Wombat Over a year ago

Also you want String a = myLocal.nextLine(); to be in the while loop so that its value changes each time

tom Over a year ago

You should change you initial question instead of creating a 'non' answer

Shahbaz Malik · Accepted Answer · 2018-04-11 08:53:48Z

class IO{
String[] myArray = new String[30000];

public void read()
{

    try {
        Scanner myLocal = new Scanner( new File("dictionary.txt"));  
        while (myLocal.hasNextLine()){

                for (int i=0; i<myArray.length; i++){
                String a = myLocal.nextLine();
                myArray[i] = a;

            }
        }

    }
    catch(IOException e){
        System.out.println(e);
    }
}

public void sort()
{   
    int n = myArray.length;
    for (int i=0; i<n-1; i++){
        for(int j=0; j<n-i-1; j++){
            if(myArray[j+1].compareTo(myArray[j])<0){
                String temp = myArray[j];
                myArray[j] = myArray[j+1];
                myArray[j+1] = temp;
                //toLower
            }
        }

    }



}

public void swap(int j, String[] arr)
{

    String temp = arr[j-1];
    arr[j-1] = arr[j];
    arr[j] = temp;
}

public void write()
{

    try{
        PrintStream writer = new PrintStream(new File("sorted.txt"));
        for (int i=0; i<myArray.length; i++){
            writer.println(myArray[i] + "\n");
            }
            writer.close();
    }
    catch(IOException e){
        System.out.println(e);
    }


}

}

Shahbaz Malik · Accepted Answer · 2018-04-12 05:11:59Z

1

CORRECT CODE (SOLVED)

class IO{

String[] myArray = new String[30000];

public void read()
{

    try {
        Scanner myLocal = new Scanner( new File("dictionary.txt"));  
        while (myLocal.hasNextLine()){

                for (int i=0; i<myArray.length; i++){
                String a = myLocal.nextLine();
                myArray[i] = a;

            }
        }

    }
    catch(IOException e){
        System.out.println(e);
    }
}

public void sort()
{   
    int n = myArray.length;

    for (int i=0; i<n; i++){
        for(int j=1; j<n-i; j++){ 
        if (myArray[j-1].compareTo(myArray[j])>0){



                swap(j, myArray);



            }

        }


    } 



}
public void swap(int j, String[] myArray)
{
    String temp = myArray[j-1];
    myArray[j-1]=myArray[j];
    myArray[j]=temp;


}

public void write()
{
    try{
        PrintStream writer = new PrintStream(new File("myIgnoreNew.txt"));
        for (int i=0; i<myArray.length; i++){
            writer.println(myArray[i] + "\n");
            }
            writer.close();
    }
    catch(IOException e){
        System.out.println(e);
    }


}

}

answered Apr 12, 2018 at 5:11

Shahbaz Malik

719 bronze badges

1 Comment

daniu Over a year ago

Try to get used to using try-with-resources for these kinds of read and write. Look it up, it's very straightforward to use and a good habit to have.

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