import java.awt.*; import java.util.*; import javax.swing.*; import java.io.*; /

Question

import java.awt.*;
import java.util.*;
import javax.swing.*;
import java.io.*;

//function
public class Exercise14_27 extends JFrame{

//constructor

public Exercise14_27() throws IOException{
System.out.print("Enter file name for the "+ "graph: ");

//input
Scanner input = new Scanner(System.in);

String filename = input.nextLine();

Scanner file = new Scanner(new File(filename));

int n= Integer.parseInt(file.nextLine());

int[][] position = new int[n][2];

ArrayList[] edge = new ArrayList[n];

//for loop

for(int i=0;i<n;i++){
String[] tokens=file.nextLine().split(" ");

//storing x,y position value into a variable

position[i][0]= Integer.parseInt(tokens[1]);
position[i][1]= Integer.parseInt(tokens[2]);

//Create a new array list

edge[i] = new ArrayList<String>();

//for loop statement

for(int k=3; k<tokens.length;k++){
edge[i].add(Integer.parseInt(tokens[k]) );
}//inner loop

}// end of for-loop

add(new GraphView(position, edge));

}//end of 14_27constructor

//main method
public static void main(String[] args) throws Exception{
Exercise14_27 frame = new Exercise14_27();
//panel size

frame.setSize(400,400);

//panel title

frame.setTitle("Exercise14_21");

//default close operation

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//frame in the center of the screen
frame.setLocationRelativeTo(null);

frame.setVisible(true);

}// end of main
}// exercise14_21

// class definition

class GraphView extends JPanel{
//declared variable

private int[][] position;
private ArrayList[] edge;

//constructor definition

public GraphView(int[][] position, ArrayList[] edge){
this.position = position;
this.edge = edge;

}// end of GraphView constructor

@Override
protected void paintComponent(Graphics g){
for(int i=0; i<position.length;i++){

//an oval on the panel
g.fillOval(position[i][0]-8, position[i][1]- 8,16,16);
g.drawString(i +"", position[i][0]-12, position[i][1]-12);
}// end of for loop

for(int i=0; i<edge.length;i++){

for(int j=0; j<edge[i].size();j++){
int v= (Integer)edge[i].get(j);
g.drawLine(position[i][0], position[i][1], position[v][0], position[v][1]);

}// end of inner one loope

}//end of outer for loop
}// end of paintComponent

}//end of GraphView

My question is, it is not reading my text file. What's wrong here???

Explanation / Answer

We cannot read a file using Scanner class.Try the following code instead.

String file_name="filename.txt";
try {
      ReadFile file= new ReadFile(file_name);
      String[] aryLines=file.OpenFile();
}
catch (IOException e)
{
System.out.println(e.getMessage() );
}
}

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