Java Reference
In-Depth Information
switch
(nextCharacter)
{
case
'(':
case
'[':
case
'{':
openDelimiterStack.push(nextCharacter);
break
;
case
')':
case
']':
case
'}':
if
(openDelimiterStack.isEmpty())
isBalanced =
false
;
else
{
char
openDelimiter =
openDelimiterStack.pop();
isBalanced = isPaired(openDelimiter, nextCharacter);
}
// end if
break
;
default
:
break
;
}
// end switch
}
// end for
if
(!openDelimiterStack.isEmpty())
isBalanced =
false
;
return
isBalanced;
}
// end checkBalance
// Returns true if the given characters, open and close, form a pair
// of parentheses, brackets, or braces.
private static boolean
isPaired(
char
open,
char
close)
{
return
(open == '(' && close == ')') ||
(open == '[' && close == ']') ||
(open == '{' && close == '}');
}
// end isPaired
}
// end BalanceChecker
The following statements provide an example of how you might use this class:
String expression = "a {b [c (d + e)/2 - f] + 1}";
boolean
isBalanced = BalanceChecker.checkBalance(expression);
if
(isBalanced)
System.out.println(expression + " is balanced");
else
System.out.println(expression + " is not balanced");
Our ultimate goal is to show you how to evaluate infix algebraic expressions, but postfix expres-
sions are easier to evaluate. So we first look at how to represent an infix expression by using
postfix notation.
