import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class yufa extends JFrame implements ActionListener
{
	int m;
	int right;
	int t=0;
	private JTextArea ta1;
	private JTextArea ta2;
	private JButton jb=new JButton("語法分析"); 
	private JButton jb1=new JButton("清空文本區(qū)");
	private JLabel  jl1=new JLabel("輸入表達式：");
	private JLabel  jl2=new JLabel("分析結(jié)果：");
	char[] c=new char[50];
	char exp[]=new char[50];
	int result;
	public yufa()
	{   
		super("語法分析器");  
		this.setSize(600,448);
		this.setLocation(200,150);
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		this.setLayout(null);
		JPanel jp =new JPanel();
		JPanel jp1 =new JPanel();
		jp.setSize(300, 400);
		jp1.setSize(300, 400);
		jp.setLocation(0, 0);
		jp1.setLocation(300, 0);
		jp.setLayout(null);
		jp1.setLayout(null);
		ta1=new JTextArea(20,30);
		ta2=new JTextArea(20,30);
		ta2.setEditable(false);
	    JScrollPane scrol1=new JScrollPane(ta1,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
	    JScrollPane scrol2=new JScrollPane(ta2,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
	            JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
	    scrol1.setSize(260, 310);
	    scrol1.setLocation(18, 40);
	    scrol2.setSize(260, 310);
	    scrol2.setLocation(18, 40);
        jp.add(scrol1);  
	    jp1.add(scrol2);
	    jb.setBounds(80, 370, 100, 25);
	    jb1.setBounds(80, 370, 100, 25);
	    jl1.setFont(new Font("楷書",Font.BOLD,12));
	    jl1.setSize(140, 25);
	    jl1.setLocation(0, 0);
	    jl2.setFont(new Font("楷書",Font.BOLD,12));
	    jl2.setSize(140, 25);
	    jl2.setLocation(0, 0);
	    jp.add(jb1);
	    jp.add(jl1);
		jp1.add(jb);
		jp1.add(jl2);
		this.add(jp);
		this.add(jp1);
		jb.addActionListener(this);
		jb1.addActionListener(this);
		this.setVisible(true);
	}
	public void actionPerformed(ActionEvent e)
	{    
		if(e.getSource()==jb1)
	    {
		   int a1=JOptionPane.showConfirmDialog(null, "確定清空嗎？","提示！",JOptionPane.YES_NO_OPTION);
		   if( a1==JOptionPane.YES_OPTION)
		   { 
			   ta1.setText("");
		       ta2.setText("");
		       result=-1;
		   }
	    }
		if(e.getSource()==jb)
		{   
			int n=0;
			right=1;
			m=0;
			String jg;
			String a=ta1.getText();
			char[] b=new char[a.length()];
			for(int i=0;i<a.length();i++)
			{
			    b[i]=a.charAt(i);
			    c[i]=a.charAt(i);
			      n=i;
			}
			for(int d=n+1;d<50;d++)
				c[d]='#';
			while(m<a.length()&&c[m]!='#'&&right==1)
			{
				if(Character.isDigit(c[m])||c[m]=='+'||c[m]=='-'||c[m]=='/'||c[m]=='*'||c[m]=='('||c[m]==')'||c[m]=='#')
				{
					e(c[m]);
				}
				else
				{
					ta2.setText("輸入不正確，請重新輸入！");
					return;
				}
				
			}
			if(c[m]=='#'&&right==1&&result!=-65535)
				{
				  ta2.setText("OK"+"\n");
			  
			      jg=String.valueOf(result);
			      ta2.setText(ta2.getText()+jg);
			    }
			else
				if(result!=-65535)
				ta2.setText("Error"+"\n");
			
		}
	}
		int e(char i)
		{
			result = t (c[m]);
			if(result==-1)
				return -1;
			 while (c[m] == '+' || c[m] == '-') 
			 {
			  if(c[m] == '+')
			  {
				  m++;
			   result += t (c[m]); 
			  }
			   else 
				   if(c[m] == '-')
				   {
					   m++;
					   result -= t (c[m]);					   
				   }
			 }
			  return result;
		}

		int t(char i)
		{
			result = f (c[m]);
			 while (c[m] == '*' || c[m] == '/') 
			 {			  
			  if(c[m] == '*') 
			  {
				  m++;
			   result *= f (c[m]); 
			  
			  }
			   else 
				   if(c[m] == '/')
				   {
					   m++;
					   if(c[m]=='0')
					   {
						   c[m]='#';
						   ta2.setText("除數(shù)不能為0，請重新輸入！");
						    return -65535;
					   }
					   else
					   result /= f (c[m]);
					   
				   }
			 }
			  return result;
		}
		
		int f(char i)
		{			
				if(c[m]=='(')
				{
					m++;
					t=e(c[m]);
					if(c[m]==')')
						m++;
					else
					{
						right=0;
					return right;
					}
					
				}
				else if(Character.isDigit(c[m]))
				{
					int n=0;
					
					char[] b=new char[5];
					b[0]=c[m];
					n=1;
					m++;
					while(Character.isDigit(c[m]))
					{
						b[n]=c[m];
						m++;
					    n++;					    
					}
					
					for(;n<5;n++)
						b[n]='#';
					t=(int)b[0]-48;
					n=1;
					while(n<5)
					{
					   if(Character.isDigit(b[n]))
					   {
						   t=t*10+((int)b[n]-48);
					       n++;
					   }
					   else
						   n=5;
					}
					
				}
				else
				{
					right=0;
					return right;
				}
				
			return t;
			
		}
		
	
	public static void main(String args[])
	{
		new yufa();
	}
}