Java 中缀表达式解算器中出现空堆栈异常
所以我的程序应该采用语法正确的中缀表达式 包含GUI中的整数操作数和四个算术运算符(+-*/),并显示结果。不幸的是,如果我输入一个简单的表达式,比如3+4,程序就会抛出一个空堆栈异常。我刚刚开始使用stacks,所以请原谅我犯了一些简单的错误。请帮忙Java 中缀表达式解算器中出现空堆栈异常,java,exception,stack,infix-notation,Java,Exception,Stack,Infix Notation,所以我的程序应该采用语法正确的中缀表达式 包含GUI中的整数操作数和四个算术运算符(+-*/),并显示结果。不幸的是,如果我输入一个简单的表达式,比如3+4,程序就会抛出一个空堆栈异常。我刚刚开始使用stacks,所以请原谅我犯了一些简单的错误。请帮忙 import javax.swing.*; import java.awt.*; import java.awt.event.*; import java.util.*; public class inFix extends JFrame {
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class inFix extends JFrame
{
private Container contents;
private JLabel infixLabel, resultLabel, result;
private JTextField infixText;
private JButton evaluate;
public inFix()
{
super("Infix Expresion Evaluator");
contents = getContentPane();
contents.setLayout( new FlowLayout() );
infixLabel = new JLabel("Enter Infix Expression:");
infixText = new JTextField("", 14);
evaluate = new JButton("Evaluate");
resultLabel = new JLabel("Result:");
result = new JLabel("???");
contents.add( infixLabel );
contents.add( infixText );
contents.add( evaluate );
contents.add( resultLabel );
contents.add( result );
ButtonHandler bh = new ButtonHandler();
evaluate.addActionListener( bh );
setSize( 350, 200 );
setVisible( true );
}
private class ButtonHandler implements ActionListener
{
public void actionPerformed( ActionEvent ae )
{
result.setText(infix(infixText.getText()));
}
}
public String infix(String expression)
{
expression=expression.replaceAll("[\t\n ]", "")+"=";
String operator = "*/+-";
int value1, value2;
char ch;
StringTokenizer tokenizer = new StringTokenizer(expression, operator, true);
Stack<Integer> valueStack = new Stack<Integer>();
Stack<Character> operatorStack = new Stack<Character>();
while(tokenizer.hasMoreTokens())
{
String token = tokenizer.nextToken();
if(isInteger(token) == true)
valueStack.push(Integer.parseInt(token));
else if(token.charAt(0) == '(')
operatorStack.push(token.charAt(0));
else if(token.charAt(0) == ')')
while(operatorStack.peek() != '(')
{
value1 = valueStack.pop();
value2 = valueStack.pop();
valueStack.push(solver(value1, value2, operatorStack.pop()));
}
else if(token.charAt(0) == '+' || token.charAt(0) == '-' || token.charAt(0) == '*' || token.charAt(0) == '/')
{
while(!operatorStack.isEmpty() && precedence(token.charAt(0)) <= precedence(operatorStack.peek()))
{
value1 = valueStack.pop();
value2 = valueStack.pop();
valueStack.push(solver(value1, value2, token.charAt(0)));
}
operatorStack.push(token.charAt(0));
}
}
while(!operatorStack.isEmpty())
{
value1 = valueStack.pop();
value2 = valueStack.pop();
ch = operatorStack.pop();
valueStack.push(solver(value1, value2, ch));
}
String result = Integer.toString(valueStack.pop());
return result;
}
public static boolean isInteger(String s)
{
try
{
Integer.parseInt(s);
}
catch(NumberFormatException e)
{
return false;
}
catch(NullPointerException e)
{
return false;
}
return true;
}
public int solver( int value1, int value2, char operator)
{
if(operator == '*')
return value1 * value2;
else if(operator == '/')
return value1 / value2;
else if(operator == '+')
return value1 + value2;
else if(operator == '-')
return value1 - value2;
else
return 0;
}
public int precedence(char op)
{
if(op == '+' || op == '-')
return 1;
else if(op == '*' || op == '/')
return 2;
else
return -1;
}
public static void main( String [] args )
{
inFix infixsolver = new inFix();
infixsolver.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
}
}
import javax.swing.*;
导入java.awt.*;
导入java.awt.event.*;
导入java.util.*;
公共类中缀扩展JFrame
{
私家货柜内容物;
私有JLabel infixLabel,resultLabel,result;
私有JTextField-infixText;
私有JButton评价;
公共中缀()
{
超级(“中缀表达式求值器”);
contents=getContentPane();
contents.setLayout(新的FlowLayout());
infixLabel=newjlabel(“输入中缀表达式:”);
infixText=新的JTextField(“,14);
evaluate=新的JButton(“evaluate”);
resultLabel=新的JLabel(“结果:”);
结果=新的JLabel(“???”);
contents.add(infixLabel);
contents.add(infixText);
内容。添加(评估);
contents.add(resultLabel);
内容。添加(结果);
ButtonHandler bh=新ButtonHandler();
evaluate.addActionListener(bh);
设置大小(350200);
setVisible(真);
}
私有类ButtonHandler实现ActionListener
{
已执行的公共无效行动(行动事件ae)
{
result.setText(infix(infixText.getText());
}
}
公共字符串中缀(字符串表达式)
{
expression=expression.replaceAll(“[\t\n]”,“)+”=”;
字符串运算符=“*/+-”;
int值1、值2;
char ch;
StringTokenizer tokenizer=新的StringTokenizer(表达式,运算符,true);
堆栈值堆栈=新堆栈();
堆栈运算符堆栈=新堆栈();
while(tokenizer.hasMoreTokens())
{
String token=tokenizer.nextToken();
如果(isInteger(令牌)=真)
push(Integer.parseInt(token));
else如果(token.charAt(0)='(')
运算符stack.push(令牌字符(0));
else if(token.charAt(0)=')')
while(运算符stack.peek()!='(')
{
value1=valueStack.pop();
value2=valueStack.pop();
valueStack.push(解算器(value1、value2、operatorStack.pop());
}
else if(token.charAt(0)='+'| | token.charAt(0)='-'| | token.charAt(0)='*'.| | token.charAt(0)='/'))
{
而(!operatorStack.isEmpty()&&priority(token.charAt(0))假设输入表达式为“3+4”
在线54
expression=expression.replaceAll("[\t\n ]", "")+"=";
expression=expression.replaceAll("[\t\n ]", "")+"=";
表达式变成“3+4=”
在标记器操作之后,标记为[“3”、“+”、“4=”],这会在第65行为标记“4=”生成错误结果
if(isInteger(token) == true)
因此,当您在第89行弹出时,值的数量是不够的
value2 = valueStack.pop();
要解决此问题,请删除第54行中的+“=”