How to print results to screen

[NinjaLink]

First I want to say that I am a Java beginner and this is my 2nd program.

I created a program that will do a symbol balance test, but I need someone to help me print the results to the screen because I am getting a blank output whenever I try to find a way to do it. I am also reading into a file. Any help is appreciated please.

test.txt looks like {{}}

For ex,

{ { } } = the symbols are equally balanced
{ [ { } = the symbols are not equally balanced

I need someone to help me find a way to print the results like

{{}} are equally balanced
or
{[}} are not equally balanced


I tried using this and placing it near the bottom of the program in between the last brackets





while (!s.empty())
{
System.out.println(s.pop());
if (failed == true)
{
System.out.println(" symbols do not match");
}
else
{
System.out.println(" The symbols match");
}





Main Program:



import java.io.* ;

public class Stackmain
{

public Stackmain()
{



}
public static boolean main(String expression) throws IOException
{

final char LEFT_PARENT = '(';
final char RIGHT_PARENT = ')';
final char LEFT_CURLY = '{';
final char RIGHT_CURLY = '}';
final char LEFT_SQUARE = '[';
final char RIGHT_SQUARE = ']';

Stack s = new Stack(100);
char ch;
int i = 0;
boolean failed = false;

FileInputStream fstream = new FileInputStream("test.txt");

DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine;

while ((ch = (char)br.read()) != (char)-1 )
if (!s.full())
{
for (i=0; !failed && (i < expression.length( )); i++)
{
switch (expression.charAt(i))
{
case LEFT_PARENT:
case LEFT_CURLY:
case LEFT_SQUARE:
s.push(expression.charAt(i));
break;
case RIGHT_PARENT:
if (s.empty() || (s.pop() != LEFT_PARENT))
failed = true;
break;
case RIGHT_CURLY:
if (s.empty() || (s.pop() != LEFT_CURLY))
failed = true;
break;
case RIGHT_SQUARE:
if (s.empty() || (s.pop() != LEFT_SQUARE))
failed = true;
break;
}
}
}
return (s.empty() && !failed);
}
}






Stack Class



class Stack {
private int maxStack;
private int emptyStack;
private int top;
private char[] items;




public Stack(int size) {
maxStack= size;
emptyStack = -1;
top = emptyStack;
items = new char[maxStack];
}



public void push(char c) {
items[++top] = c;
}

public char pop() {
return items[top--];
}

public boolean full() {
return top + 1 == maxStack;
}

public boolean empty() {
return top == emptyStack;
}
}

[NinjaLink]

I still receive a blank screen when I try to print...

My latest modification to try to print is below:



import java.io.* ;

public class Stackmain
{

// public Stackmain()
// {


// }
public static boolean main(String expression) throws IOException
{

final char LEFT_PARENT = '(';
final char RIGHT_PARENT = ')';
final char LEFT_CURLY = '{';
final char RIGHT_CURLY = '}';
final char LEFT_SQUARE = '[';
final char RIGHT_SQUARE = ']';

Stack s = new Stack(100);
char ch;
int i = 0;
boolean failed = false;

FileInputStream fstream = new FileInputStream("test.txt");

DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));



while ((ch = (char)br.read()) != (char)-1 )
{
if (!s.full())
{

for (i=0; !failed && (i < expression.length( )); i++)
{
switch (expression.charAt(i))
{
case LEFT_PARENT:
case LEFT_CURLY:
case LEFT_SQUARE:
s.push(expression.charAt(i));
break;
case RIGHT_PARENT:
if (s.empty() || (s.pop() != LEFT_PARENT))
failed = true;
break;
case RIGHT_CURLY:
if (s.empty() || (s.pop() != LEFT_CURLY))
failed = true;
break;
case RIGHT_SQUARE:
if (s.empty() || (s.pop() != LEFT_SQUARE))
failed = true;
break;


}

}
}

}


if (failed == true)
{
System.out.println("Expression does not match");
}
if (failed == false)
{
System.out.println("Expression does match");
}

return (s.empty() && !failed);
}
}

[keang]

You're getting a blank screen because you aren't running anything. To run your class you need a main method with this signature:
public static void main(String[] args)

Whilst looking at the code I also noticed

You are reading in a file and then not doing anything with the character you've just read in.
You are using a stack but never putting anything into it.
A better way to write the print out is section is:
if (failed)
{
System.out.println("Expression does not match");
}
else
{
System.out.println("Expression does match");
}

[NinjaLink]

Thank you for the reply. I will look into it now. I appreciate it!

[NinjaLink]

3 errors:
cannot find symbol variable expression
cannot return a value from method whose result type is void
variable expression might not have been initialized


Question: When I deleted public static boolean main(String expression), I was using expression in my for loop before. Is there something that I can use to replace it?


Here is my latest code:




import java.io.* ;

class Stackmain
{
public static void main(String[] args) throws IOException
{

final char LEFT_PARENT = '(';
final char RIGHT_PARENT = ')';
final char LEFT_CURLY = '{';
final char RIGHT_CURLY = '}';
final char LEFT_SQUARE = '[';
final char RIGHT_SQUARE = ']';

Stack s = new Stack(100);
char ch;
// String expression;
int i = 0;
boolean failed = false;

FileInputStream fstream = new FileInputStream("test.txt");

DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));



while ((ch = (char)br.read()) != (char)-1 )
{
if (!s.full())
{

for (i=0; !failed && (i < expression.length( )); i++)
{
switch (expression.charAt(i))
{
case LEFT_PARENT:
case LEFT_CURLY:
case LEFT_SQUARE:
s.push(expression.charAt(i));
break;
case RIGHT_PARENT:
if (s.empty() || (s.pop() != LEFT_PARENT))
failed = true;
break;
case RIGHT_CURLY:
if (s.empty() || (s.pop() != LEFT_CURLY))
failed = true;
break;
case RIGHT_SQUARE:
if (s.empty() || (s.pop() != LEFT_SQUARE))
failed = true;
break;


}

}
}

}


if (failed == true)
{
System.out.println("Expression does not match");
}
if (failed == false)
{
System.out.println("Expression does match");
}

//return (s.empty() && !failed);
}
}

[keang]

I was using expression in my for loop before. Is there something that I can use to replace it?
public static void main(String[] args) throws IOException
{
String expression = null;

if ( args.length > 0 )
{
expression = args[0];
}

...