我有一种方法可以检查写出的方程式是否正确。
此方法检查:
- 多括号
- 多余的运算符
- 两位数
- q的
- 以及字符串中的任何字符,而不是这些字符:
.
private static final String operators = "-+/*%_";
private static final String operands = "0123456789x";
它工作正常,但后来我以模块化方式添加到运算符中,现在每当我的代码到达方法中检查操作数左右两侧的部分时,它是否既不是字符串的结尾也不是开头我收到一条错误消息
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 3
我的方法和所有它的附加方法。
private static final String operators = "-+/*%_";
private static final String operands = "0123456789x";
public Boolean errorChecker(String infixExpr)
{
char[] chars = infixExpr.toCharArray();
StringBuilder out = new StringBuilder();
for (int i = 0; i<chars.length; i++)
{
System.out.print(infixExpr.charAt(i));
if (isOperator(infixExpr.charAt(i)))
{
if (i == 0 || i == infixExpr.length())
{
out.append(infixExpr.charAt(i));
}
else if (isOperator(infixExpr.charAt(i + 1)) && isOperator(infixExpr.charAt(i - 1)))
{
System.out.println("To many Operators.");
return false;
}
else if (isOperator(infixExpr.charAt(i + 1)))
{
if (infixExpr.charAt(i) != '-' || infixExpr.charAt(i + 1) != '-')
{
System.out.println("To many Operators.");
return false;
}
}
else if (isOperator(infixExpr.charAt(i - 1)))
{
if (infixExpr.charAt(i) != '-' || infixExpr.charAt(i - 1) != '-')
{
System.out.println("To many Operators.");
return false;
}
}
}
else if (isOperand(infixExpr.charAt(i)))
{
if (i == 0 || i == infixExpr.length())
{
out.append(infixExpr.charAt(i));
}//THE LINE RIGHT BELOW THIS COMMENT THROWS THE ERROR!!!!!
else if (isOperand(infixExpr.charAt(i + 1)) || isOperand(infixExpr.charAt(i - 1)))
{
System.out.println("Double digits and Postfix form are not accepted.");
return false;
}
}
else if (infixExpr.charAt(i) == 'q')
{
System.out.println("Your meow is now false. Good-bye.");
System.exit(1);
}
else if(infixExpr.charAt(i) == '(' || infixExpr.charAt(i) == ')')
{
int p1 = 0;
int p2 = 0;
for (int p = 0; p<chars.length; p++)
{
if(infixExpr.charAt(p) == '(')
{
p1++;
}
if(infixExpr.charAt(p) == ')')
{
p2++;
}
}
if(p1 != p2)
{
System.out.println("To many parentheses.");
return false;
}
}
else
{
System.out.println("You have entered an invalid character.");
return false;
}
out.append(infixExpr.charAt(i));
}
return true;
}
private boolean isOperator(char val)
{
return operators.indexOf(val) >= 0;
}
private boolean isOperand(char val)
{
return operands.indexOf(val) >= 0;
}
我运行该方法的主要部分:
Boolean meow = true;
while(meow)
{
System.out.print("Enter infix expression: ");
infixExpr = scan.next();//THE LINE RIGHT BELOW THIS COMMENT THROWS THE ERROR!!!!!
if(makePostfix.errorChecker(infixExpr) == true)
{
System.out.println("Converted expressions: "
+ makePostfix.convert2Postfix(infixExpr));
meow = false;
}
}
它以前工作得很好,但现在它甚至不会通过以前工作的 1+2,我没有改变你看到的。怎么了!?!?