编译原理语法分析算术表达式.doc

package 语法分析;public class displymain public static void main(String args) new frame();package 语法分析;import java.awt.GridLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.*;public class frame implements ActionListenerJFrame frame1;JLabel L1,L2;JButton bt,bt2;JTextField input,result;top_down_grammar a =new top_down_grammar();public frame()frame1=new JFrame();input=new JTextField(20);result=new JTextField(20);L1=new JLabel(请输入表达式以#结束);L2=new JLabel(结果是：);bt=new JButton(语法分析);bt2=new JButton(关闭);frame1.setTitle(递归下降子程序分析语法);frame1.setLayout(new GridLayout(3,1);frame1.add(L1);frame1.add(input);frame1.add(L2);frame1.add(result);frame1.add(bt);frame1.add(bt2);bt.addActionListener(this);bt2.addActionListener(this);frame1.setSize(500, 500);frame1.setVisible(true);public void actionPerformed(ActionEvent e)a.i=0;a.x.str=input.getText();if(e.getActionCommand()=语法分析) if(a.E_Production() result.setText(符合语法要求);else result.setText(不符合语法要求);if(e.getActionCommand()=关闭) frame1.dispose();package 语法分析;public class Lex String str=; int i;/int j=0; public char lex(int j) i=j;if(is_identifiers_key()return 2;if(is_digital()return 1;if(is_oper()return str.charAt(i);return 0;public boolean is_identifiers_key()boolean f=false;/c2=str.charAt(i);while(i=65&str.charAt(i)=97&str.charAt(i)=122)|(str.charAt(i)=_)i+;f=true;if(f)i-;return f;public boolean is_digital() boolean f=false; if(i=48&str.charAt(i)=48&str.charAt(i)=57)|str.charAt(i)=.) i+; f=true; /c=(str.charAt(i); if(f) i-; return f; return false;public boolean is_oper() / c2=str.charAt(i);if(istr.length() if(str.charAt(i)=(|str.charAt(i)=)|str.charAt(i)=+|str.charAt(i)=-|str.charAt(i)=*|str.charAt(i)=/|str.charAt(i)=#) return true; return false;package 语法分析;public class top_down_grammar char ch;int i=0;Lex x=new Lex();public boolean E_Production() ch=x.lex(i); if(ch=+ |ch=-) i=x.i; i+; ch=x.lex(i); if(!T_Production() return false; if(!G_Production() return false; return true; public boolean T_Production()if( !F_Production() return false;if(!S_Production() return false;return true;public boolean F_Production()if(ch=() i=x.i;i+; ch=x.lex(i); if(E_Production()return false;if(ch=)i=x.i;i+; ch=x.lex(i); return true;else return false;if(ch=1|ch=2) i=x.i;i+; ch=x.lex(i); return true;else return false;public boolean G_Production()if(ch=+)i=x.i;i+; ch=x.lex(i); if(!T_Production() return false;if(!G_Production() return false;return true;else if(ch=-)i=x.i;i+; ch=x.lex(i); if(!T_Production() return false;if(G_Production() return false;return true;else if(ch=)|ch=#)return true;return false;public boolean S_Production()if(ch=*)i=x.i;i+; ch=x.lex(i); if(!F_Production() return false;if(!S_Production() return false;return true;else if(ch=/)i=x.i;i+; ch=x.lex(i); if(!F_Production() return false;if(!S_Production() return fa