Question

Modify the program so that it uses a loops repeatedly doing:
• prompt for input (using line seqNum and the prompt phrase: "Enter a line")
• reads the line of input
• stores the line of input in the next position of an array of Line or
an ArrayList of Line.
Once the user enters STOP as input, the loop should terminate and another loop should
print each line in reverse order. For example (the input you should type in is in bold):
1: Enter a line
Some input
2: Enter a line
More input
3: Enter a line
The end
4: Enter a line
STOP
3: The end
2: More input
1: Some input
Hints:
To create an array of Line and add to it, assuming there will be no more than 10 lines, use:
Line[] lineStore = new Line[10];
...
lineStore[n] = msg; // where msg is an object of type Line
...
lineStore[0]; // to get the Line object at position 0;
or to create an ArrayList of Line use:
ArrayList<Line> lineStore = new ArrayList<Line>();
...
lineStore.add(msg); // where msg is an object of type Line
...
lineStore.get(0); // to get the Line object at position 0

My previous code:

public class P1 {

/**
* @param args the command line arguments
*/
public static void main(String[] args) {

final int maxnum = 3;
Line[] lineStore = new Line[maxnum];
Scanner in = new Scanner(System.in);
for (int i = 0; i < maxnum; i++) {
String msg = in.nextLine();
lineStore[i] = new Line(i + 1, msg);//start with 1 now
}
  
for (int i = lineStore.length-1; i >= 0; i--) {//i = 2
if (i != 0) {
System.out.print(lineStore[i].getSeqNum() + ": " + lineStore[i].getText()+ ",");
} else {
System.out.print(lineStore[i].getSeqNum() + ": " + lineStore[i].getText());

}
}
}

public class Line {
private int seqNum;
private String text;

public Line(int seqNum, String text) {
this.seqNum = seqNum;
this.text = text;
}

public int getSeqNum() {
return seqNum;
}

public String getText() {
return text;
}

  
}

Answer 1

//Java program

import java.util.ArrayList;
import java.util.Scanner;
class Line {
   private int seqNum;
   private String text;

   public Line(int seqNum, String text) {
   this.seqNum = seqNum;
   this.text = text;
   }

   public int getSeqNum() {
   return seqNum;
   }

   public String getText() {
   return text;
   }

  
   }

public class P1 {

  

   public static void main(String[] args) {

       ArrayList<Line> lineStore = new ArrayList<Line>();
      
       Scanner in = new Scanner(System.in);
       int i=1;
       boolean valid=true;
       do {
           System.out.println(i+":Enter a line");
           String msg = in.nextLine();
           if(msg.compareToIgnoreCase("STOP")==0)
               valid = false;
              
           if(valid)lineStore.add( new Line(i, msg));
          
           i++;
       }while(valid);
      
       for ( i = lineStore.size()-1; i >= 0; i--)
               System.out.println(lineStore.get(i).getSeqNum() + ": " + lineStore.get(i).getText());
      
      
       in.close();
       }
      
}

//sample output