Thread: Spaceship question...

A spaceship has to travel a distance of 1500 miles away from earth. The spaceship can only travel 220 miles before it needs to refuel. It is fueled before it leaves earth and there are several fueling stations along the way. Read data from a file where the end of data is indicatded by a distance of 0 as follows:

912
510
400
0

Another set of sample data could be:
1280
720
900
1400
500
200
360
1100
0

the program should output to the user whether or not the journey is possible. For the 1st set of sample data, the journey is not possible but it is possible for the second set.

Can someone tell me how to go about doing this please.

I would say:
1) Read the file
2) Parse the lines of text within the file
3) Calculate whether the journey is possible or not
4) Output results to user

Now, you should think about these steps one by one and try to implement them.

What do the numbers represent? Distance of fueling stations from Earth along a straight line to the destination?

Originally Posted by GregBrannon

What do the numbers represent? Distance of fueling stations from Earth along a straight line to the destination?

yes the numbers represent fueling stations from Earth to the destination. Is there a way to read those values into an array without knowing the size of the array

--- Update ---

Originally Posted by Cornix

I would say:
1) Read the file
2) Parse the lines of text within the file
3) Calculate whether the journey is possible or not
4) Output results to user

Now, you should think about these steps one by one and try to implement them.

this does not help...

Is there a way to read those values into an array without knowing the size of the array

Yes, but can you use an ArrayList?

Originally Posted by GregBrannon

Yes, but can you use an ArrayList?

I dont know what is an array list. We just did basic arrays in class so i dont think i can use that.

Originally Posted by Norm

You could use an array if you made it large enough that you could be sure that the data wouldn't overflow it.

this is what i tried but its only displaying the same number.

	public static void main (String [] args) throws IOException{
		Scanner in = new Scanner(new FileReader("distances.txt"));	
 
int [] distance = new int [100];
int dist=in.nextInt();
while (dist!=0){
 
for(int i=0;i<distance.length;i++){
	distance[i]=dist;
}
 
dist=in.nextInt();
}//end while
int i;
for(i=0;i<distance.length;i++)
System.out.printf("%d\n",distance[i]);
	}//end main
}//end class

Originally Posted by Norm

Please edit the code and format it. Logically nested statements should be indented.


Please post the program's output that shows what you are talking about.

public static void main (String [] args) throws IOException{
		Scanner in = new Scanner(new FileReader("distances.txt"));	
 
int [] distance = new int [100];
int dist=in.nextInt();
 
   while (dist!=0){
	          for(int i=0;i<distance.length;i++){
	           distance[i]=dist;
	         }//end for
 
dist=in.nextInt();
}//end while
 
System.out.printf("%d",distance[0]);
}//end main

i want to read all the numbers from the file and be able to print them to the screen. I tried testing it by just printing the first value which from the file is 1200 however it only prints the last value in the file which is 1100.

Originally Posted by javaman1

   while (dist!=0){
	          for(int i=0;i<distance.length;i++){
	           distance[i]=dist;
	         }//end for
 
dist=in.nextInt();
}//end while

Can you explain to us what exactly you are trying to do within these lines?
By the way, it would be nice if you could correctly format your code like the java standards dictate.

Originally Posted by Cornix

Can you explain to us what exactly you are trying to do within these lines?
By the way, it would be nice if you could correctly format your code like the java standards dictate.

the file im reading from consists of several integers. the last value is zero. so im trying to read the values. zero is the end of file value so i must stop reading the data when a zero is encountered

Originally Posted by Norm

If you want help you should follow the suggestions that were made:
1) format the code
2) debug it by adding some printlns

ok i added some printlsn and i made some progress. not too sure how to format the code like you said.

but the program is now reading all the data and displaying it. however after it is displayed im getting an error at the end. here is the error:

1280
720
900
1400
500
200
360
1100
Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:907)
at java.util.Scanner.next(Scanner.java:1530)
at java.util.Scanner.nextInt(Scanner.java:2160)
at java.util.Scanner.nextInt(Scanner.java:2119)
at distances.main(distances.java:12)

Process completed.

Originally Posted by Norm

Please post the new code with the formatting and the printlns so we can see what the code is doing.


Look at other code that has been posted on the forum. Most of it is properly formatted.
Here is a sample:

      // loop until only one left
      while(nbrLeft > 1) {
         //  go around players nW times / remove player when at end
         int wordCnt = nW-1;          //  0 to count-1
         if(idx == players.length)
            idx = 0;  // wrap around
 
         //  need this loop to skip over removed players
         while(wordCnt >= 0) {
            // move from alive element to alive element for wordCnt times
            if(players[idx++] == Live) { // alive ?
               if(wordCnt == 0) {     //  at the end of the words?
                  players[idx-1] = Removed;  // remove
                  nbrLeft--;                 // count down players
                  System.out.println("removed "+ (idx-1) + " " +Arrays.toString(players));
                  break;      //>>>>>>>>>> exit word count loop
               }
               wordCnt--;       // count words
            }
            if(idx == players.length)
               idx = 0;   // wrap index around
         }   // end while() going through words
 
      }  // end while() until 1 left

ok i made some changes and now the program is reading all the values but it is displaying each value 4 times.ow can i fix it so that it only displays each value once?

int [] distance = new int [10];//array of size 10
int dist=in.nextInt();//read first value from file
 
while (dist!=0){//while value is not equal to 0 do
 
	      for(int i=0;i<distance.length;i++){//loops from 1st value to last value
	            distance[++i]=dist;//set dist to 1st location in array
 
            	System.out.printf("%d\n",distance[i]);//display value
	      }//end for
	     dist=in.nextInt();//read next value
       }//end while
 
in.close();
}//end main
	}//end class

Originally Posted by Norm

Please post the program's print out.

The last 3 lines of the code are not properly formatted.
There are many lines that are not properly aligned.
The } should be in line in the same column below the start of the line with the {

int [] distance = new int [10];//array of size 10
int dist=in.nextInt();//read first value from file
 
while (dist!=0){//while value is not equal to 0 do
 
	      for(int i=0;i<distance.length;i++){//loops from 1st value to last value
	            distance[++i]=dist;//set dist to 1st location in array
 
            	System.out.printf("%d\n",distance[i]);//display value
	      }//end for
	     dist=in.nextInt();//read next value
       }//end while
 
            in.close();
            }//end main
        }//end class
1280
1280
1280
1280
1280
720
720
720
720
720
900
900
900
900
900
1400
1400
1400
1400
1400
500
500
500
500
500
200
200
200
200
200
360
360
360
360
360
1100
1100
1100
1100
1100
 
Process completed.

Originally Posted by Norm

The code inside of a for loop should NOT change the value of the loop's index:

for(int i=0;i<distance.length;i++){//loops from 1st value to last value
    distance[++i]=dist;  //<<<NO don't change i here (i++), the for does it

What is the purpose of the for loop inside of the while loop?
Why do you want to set ALL of the values in the array to the value in dist?

I want to store all the values from the text file into the array.

Originally Posted by Norm

Ok, what simple steps should the code take to do that? Can you make a list of the steps that can be used as a guide to write the code?

i read the values into the array but its displaying each value 4 times. thats my only problem