Output of numbers are incorrect sometimes.

**soupi** · October 24th, 2013, 08:43 AM

Hi I am trying to do a simple java code which outputs a number if i add 4 letters. When I do different combinations like d-c+a+b it gives me a inccorect number like 118.0. Can someone tell me where in my code my calculations are wrong..

Thank you

the ValVarPairs.txt contains these numbers-> a=100,b=5,c=10,d=13

and below is the code I have.

package com.ecsgrid;
 
import java.io.*;
 
public class testC {
 
public static void main(String[] args) {
  int i = 0,j = 0;
  double result, values[] = new double[4];
  char k, operators[] = new char[3];
  for (i = 0; i <= 2; i++) 
    operators[i] = '+';      // default is to add the values
 
  File myfile;
  StreamTokenizer tok;
  BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
  String InputText;
 
  i = 0;
  try {
    myfile = new File("C:\\VarValPairs.txt");
    tok = new StreamTokenizer(new FileReader(myfile));  
    tok.eolIsSignificant(false);
 
    while ((tok.nextToken() != StreamTokenizer.TT_EOF) && (i <= 3)){
      if ((tok.ttype == StreamTokenizer.TT_NUMBER))
        values[i++] = tok.nval;
      }
  }
  catch(FileNotFoundException e) { System.err.println(e);  return; }
  catch(IOException f) { System.out.println(f); return; }
 
  System.out.println("Enter letters and operators:");
 
  try {
    InputText = in.readLine(); 
  }  
  catch(IOException f) { System.out.println(f); return; }
 
  for (i = 0; i < InputText.length(); i++)
  {
     k = InputText.charAt(i);
     if ((k == '+') || (k == '-'))
     {
        if (j <= 2) operators[j++] = k;   
     }
  } 
 
  result = values[0];
  for (i = 0; i <= 2; i++){
   if (operators[i] == '+')
     result = result + values[i+1];  
   else
     result = result - values[i+1];
  }
  System.out.println(result);  
 }
}

**Norm** · October 24th, 2013, 08:46 AM

Can you copy the contents of the command prompt window from when you execute the program that shows how the program is executed and what the program prints out when it executes?

To copy the contents of the command prompt window:
Click on Icon in upper left corner
Select Edit
Select 'Select All' - The selection will show
Click in upper left again
Select Edit and click 'Copy'

Paste here.

**soupi** · October 24th, 2013, 08:51 AM

Thank you for your quick reply Norm.

I copied the output I received in Console:

Enter letters and operators:
d-c+a+b
118.0

Is this what you wanted?

**Norm** · October 24th, 2013, 08:56 AM

gives me a inccorect number like 118.0

What is the correct answer?

**soupi** · October 24th, 2013, 09:00 AM

In the console when I did d-c+a+b it gave me 118.0
It was suppose to give me 108

**Norm** · October 24th, 2013, 09:05 AM

Time to start debugging to see where the code is going wrong. Add some println statements to print out the values of the variables as the code executes so you can see where the code is going wrong.

**soupi** · October 24th, 2013, 09:10 AM

hi i just started doing java this week

, how would I do a println statment and where would I add it?
thanks

**Norm** · October 24th, 2013, 09:14 AM

how would I do a println statment

Here is a sample from your code:

  System.out.println(result);

I'd change it to include an id string so you know which println's output you are seeing:

  System.out.println("1res="+result); // print value of result with id

Change the 1 to a different value for each println you add.

Add a println that prints out the value of result after EVERY statement that changes the value of result so you can see what values the program is assigning to result every time its value is changed.

**soupi** · October 24th, 2013, 09:21 AM

so I would add System.out.println to if (j <= 2) operators[j++] = k;
and
operators[i] = '+'; ?

**Norm** · October 24th, 2013, 09:27 AM

Start with printing out the value of the one variable: result and see what is printed. If that doesn't help, you can always add more println statements for other variables.

**soupi** · October 24th, 2013, 09:31 AM

ok can you give me another example of where I would put the first print statment in my code?

**Norm** · October 24th, 2013, 09:36 AM

Put a println statement AFTER EVERY line where the variable result is assigned a value:

  result = someValue;  //  this statement assigns result a value
  System.out.println("1res="+result); // print value of result with id

**soupi** · October 24th, 2013, 10:00 AM

I still couldnt debug it, do you know why its giving me wrong input?

**Norm** · October 24th, 2013, 10:03 AM

Don't give up on debugging the code. You will have to know how to debug for all the programs that you write.

What did the debug println statements print out?
Copy and paste what is printed out and the new version of the program that has the println() statements so we can correlate the print out with where in the program it was printed.

**soupi** · October 24th, 2013, 10:08 AM

package com.ecsgrid;

import java.io.*;

public class testC {

public static void main(String[] args) {
int i = 0,j = 0;
double result, values[] = new double[4];
char k, operators[] = new char[3];
for (i = 0; i <= 2; i++)
operators[i] = '+'; // default is to add the values

File myfile;
StreamTokenizer tok;
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
String InputText;

i = 0;
try {
myfile = new File("C:\\VarValPairs.txt");
tok = new StreamTokenizer(new FileReader(myfile));
tok.eolIsSignificant(false);

while ((tok.nextToken() != StreamTokenizer.TT_EOF) && (i <= 3)){
if ((tok.ttype == StreamTokenizer.TT_NUMBER))
values[i++] = tok.nval;
}
}
catch(FileNotFoundException e) { System.err.println(e); return; }
catch(IOException f) { System.out.println(f); return; }

System.out.println("Enter letters and operators:");

try {
InputText = in.readLine();
}
catch(IOException f) { System.out.println(f); return; }

for (i = 0; i < InputText.length(); i++)
{
k = InputText.charAt(i);
if ((k == '+') || (k == '-'))
{
if (j <= 2) operators[j++] = k;
}
}

result = values[0];
System.out.println("1res="+result);

for (i = 0; i <= 2; i++){

if (operators[i] == '+')
result = result + values[i+1];
System.out.println("1res="+result);
else
result = result - values[i+1];
System.out.println("1res="+result);
}
System.out.println("1res="+result);
}
}

**Norm** · October 24th, 2013, 10:12 AM

What printed out?

All the println()s have the same id String: "1res" so you won't be able to tell which println printed which line of output. Change them so that are all different: 1res, 2res, 3res, 4res etc

Don't forget to wrap the posted code in code tags.

ONE PROBLEM I see in the code is that there aren't {}s to enclose the code in the if and else statements. You should ALWAYS wrap code in if and else statements in {} to prevent the problem this code is having.

**soupi** · October 24th, 2013, 10:22 AM

Enter letters and operators:
A+a+a+a
1res=100.0
2res=100.0

it is suppose to be 400 for the output.

--- Update ---

Also your saying after I put if or else put {} right after?

**Norm** · October 24th, 2013, 10:25 AM

You need to update the code and post the new version with the changed id strings and the added {}s following the if and else statements.

**soupi** · October 24th, 2013, 10:30 AM

package com.ecsgrid;
 
import java.io.*;
 
public class testC {
 
public static void main(String[] args) {
  int i = 0,j = 0;
  double result, values[] = new double[4];
  char k, operators[] = new char[3];
  for (i = 0; i <= 2; i++) 
    operators[i] = '+';      // default is to add the values
 
  File myfile;
  StreamTokenizer tok;
  BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
  String InputText;
 
  i = 0;
  try {
    myfile = new File("C:\\VarValPairs.txt");
    tok = new StreamTokenizer(new FileReader(myfile));  
    tok.eolIsSignificant(false);
 
    while ((tok.nextToken() != StreamTokenizer.TT_EOF) && (i <= 3)){
      if ((tok.ttype == StreamTokenizer.TT_NUMBER)){
        values[i++] = tok.nval;
      }
  }
  }
  catch(FileNotFoundException e) { System.err.println(e);  return; }
  catch(IOException f) { System.out.println(f); return; }
 
  System.out.println("Enter letters and operators:");
 
  try {
    InputText = in.readLine(); 
  }  
  catch(IOException f) { System.out.println(f); return; }
 
  for (i = 0; i < InputText.length(); i++)
  {
     k = InputText.charAt(i);
     { if ((k == '+') || (k == '-'))
     {
        if (j <= 2) operators[j++] = k;   
     }
  } 
 
  result = values[0];
  System.out.println("1res="+result);
 
  for (i = 0; i <= 2; i++){
 
   if (operators[i] == '+')
 
     result = result + values[i+1];  
 
 
   else {
     result = result - values[i+1];
  }
  System.out.println("2res="+result);  
 }
}
}
}

**Norm** · October 24th, 2013, 10:50 AM

There are 2 places where result gets assigned a value that don't have println() statements in the code in post#19 that did have them in post#15. You need to have println() statements after ALL the places where the value of result is change.

The else now has {}s but the if does not. You need to add {}s for the if also.

Also the poor formatting of the code makes it very hard to see which } goes with its pairing {. There should not be two }s one directly above the other.
The nested one should be indented 3-4 spaces.

**soupi** · October 24th, 2013, 10:59 AM

package com.ecsgrid;
 
import java.io.*;
 
public class testC {
 
public static void main(String[] args) {
  int i = 0,j = 0;
  double result, values[] = new double[4];
  char k, operators[] = new char[3];
  for (i = 0; i <= 2; i++) 
    operators[i] = '+';      // default is to add the values
 
  File myfile;
  StreamTokenizer tok;
  BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
  String InputText;
 
  i = 0;
  try {
    myfile = new File("C:\\VarValPairs.txt");
    tok = new StreamTokenizer(new FileReader(myfile));  
    tok.eolIsSignificant(false);
 
    while ((tok.nextToken() != StreamTokenizer.TT_EOF) && (i <= 3)){
      if ((tok.ttype == StreamTokenizer.TT_NUMBER)){
        values[i++] = tok.nval;
      }
  }
  }
  catch(FileNotFoundException e) { System.err.println(e);  return; }
  catch(IOException f) { System.out.println(f); return; }
 
  System.out.println("Enter letters and operators:");
 
  try {
    InputText = in.readLine(); 
  }  
  catch(IOException f) { System.out.println(f); return; }
 
  for (i = 0; i < InputText.length(); i++)
  {
     k = InputText.charAt(i);
     if ((k == '+') || (k == '-')){
 
       { if (j <= 2) operators[j++] = k;   
     }
  } 
 
  result = values[0];
  System.out.println("1res="+result);
 
  for (i = 0; i <= 2; i++){
 
   if (operators[i] == '+'){
 
     result = result + values[i+1];    System.out.println("2res="+result);
 
   }
   else {
     result = result - values[i+1];
  }
  System.out.println("2res="+result);  
 }
}
}
}

I tried to run it and the code keeps going.
btw thank you for your patience.

**Norm** · October 24th, 2013, 11:01 AM

What prints out when the program executes?

The ids are not unique. I see res2 in two different places.
Also there isn't a println() in the else

Also there needs to be a println() outside the loop for the final value of result.

**soupi** · October 24th, 2013, 11:08 AM

package com.ecsgrid;
 
import java.io.*;
 
public class testC {
 
public static void main(String[] args) {
  int i = 0,j = 0;
  double result, values[] = new double[4];
  char k, operators[] = new char[3];
  for (i = 0; i <= 2; i++) 
    operators[i] = '+';      // default is to add the values
 
  File myfile;
  StreamTokenizer tok;
  BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
  String InputText;
 
  i = 0;
  try {
    myfile = new File("C:\\VarValPairs.txt");
    tok = new StreamTokenizer(new FileReader(myfile));  
    tok.eolIsSignificant(false);
 
    while ((tok.nextToken() != StreamTokenizer.TT_EOF) && (i <= 3)){
      if ((tok.ttype == StreamTokenizer.TT_NUMBER)){
        values[i++] = tok.nval;
      }
  }
  }
  catch(FileNotFoundException e) { System.err.println(e);  return; }
  catch(IOException f) { System.out.println(f); return; }
 
  System.out.println("Enter letters and operators:");
 
  try {
    InputText = in.readLine(); 
  }  
  catch(IOException f) { System.out.println(f); return; }
 
  for (i = 0; i < InputText.length(); i++)
  {
     k = InputText.charAt(i);
     if ((k == '+') || (k == '-')){
 
       { if (j <= 2) operators[j++] = k;   
     }
  } 
 
  result = values[0];
  System.out.println("1res="+result);
 
  for (i = 0; i <= 2; i++){
 
   if (operators[i] == '+'){
 
     result = result + values[i+1];    System.out.println("2res="+result);
 
   }
   else {
     result = result - values[i+1];   System.out.println("3res="+result);  
 
  }
 }
}
 
 
{System.out.println("4res="+result);  
}

I did what u asked and the last } has a red X next to it

**Norm** · October 24th, 2013, 11:40 AM

Why is there a { on the next to last line?

Check that all the }s have a pairing {.

In general there should NOT be any code on the same line following a {.
Also only put one statement per line. The println statements should be on their own lines, not on the same line with another statement.

**soupi** · October 24th, 2013, 11:51 AM

package com.ecsgrid;
 
import java.io.*;
 
public class testC {
 
public static void main(String[] args) {
  int i = 0,j = 0;
  double result, values[] = new double[4];
  char k, operators[] = new char[3];
  for (i = 0; i <= 2; i++) 
    operators[i] = '+';      // default is to add the values
 
  File myfile;
  StreamTokenizer tok;
  BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
  String InputText;
 
  i = 0;
  try {
    myfile = new File("C:\\VarValPairs.txt");
    tok = new StreamTokenizer(new FileReader(myfile));  
    tok.eolIsSignificant(false);
 
    while ((tok.nextToken() != StreamTokenizer.TT_EOF) && (i <= 3)){
      if ((tok.ttype == StreamTokenizer.TT_NUMBER)){
        values[i++] = tok.nval;
      }
  }
  }
  catch(FileNotFoundException e) { System.err.println(e);  return; }
  catch(IOException f) { System.out.println(f); return; }
 
  System.out.println("Enter letters and operators:");
 
  try {
    InputText = in.readLine(); 
  }  
  catch(IOException f) { System.out.println(f); return; }
 
  for (i = 0; i < InputText.length(); i++)
  {
     k = InputText.charAt(i);
     if ((k == '+') || (k == '-'))
     {
 
       { if (j <= 2) operators[j++] = k;   
     }
  } 
 
  result = values[0];
  System.out.println("1res="+result);
 
  for (i = 0; i <= 2; i++)
  {
 
   if (operators[i] == '+')
  }
  {
     result = result + values[i+1];    
     System.out.println("2res="+result);
 
   }
   else {
     result = result - values[i+1];   
     System.out.println("3res="+result);  
}
     {
System.out.println("4res="+result);  
}

I am still getting the x's this is getting so frustrating. Maybe I shouldn't attempt to learn Java. I just dont know

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