scantest.java

词法分析器 词法分析 lex java编写

/*
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 * and open the template in the editor.
 */
import java.util.Scanner;
import java.util.ArrayList;
/**
 *
 * @author zhaowei
 */
public class ScanTest {
    private boolean error = false;
    public void newTest() {
        Scanner scanner = new Scanner(System.in);
        ArrayList<Result> result = scan(scanner.nextLine().toLowerCase()+" ");
        if(!error) {
            for(Result current : result) {
                System.out.println(current.toString());
            }
        }
    }
    public ArrayList<Result> scan(String input) {
        ArrayList<Result> result = new ArrayList<Result>();
        int index = 0;
        while(index<input.length()-1) {
            while(input.charAt(index)==' ') {
                if(index==input.length()-1)
                    return result;
                index++;
            }
            if(input.charAt(index)<='z'&&input.charAt(index)>='a') {
                int startIndex = index;
                index++;
                while((input.charAt(index)>='a'&&input.charAt(index)<='z')||(input.charAt(index)>='0'&&input.charAt(index)<='9')) {
                    index++;
                }
                if(input.substring(startIndex,index).equals("if")) {
                    result.add(new Result("if","-"));
                }
                else if(input.substring(startIndex,index).equals("then")) {
                    result.add(new Result("then","-"));
                }
                else if(input.substring(startIndex,index).equals("else")) {
                    result.add(new Result("else","-"));
                }
                else if(input.substring(startIndex,index).equals("while")) {
                    result.add(new Result("while","-"));
                }
                else if(input.substring(startIndex,index).equals("do")) {
                    result.add(new Result("do","-"));
                }
                else {
                    result.add(new Result("IDN",input.substring(startIndex,index)));
                }
            }
            else if(input.charAt(index)>='1'&&input.charAt(index)<='9') {
                int startIndex = index;
                index++;
                while(input.charAt(index)>='0'&&input.charAt(index)<='9') {
                    index++;
                }
                result.add(new Result("INT10",input.substring(startIndex,index)));
            }
            else if(input.charAt(index)=='0') {
                int startIndex = index;
                index++;
                if(input.charAt(index)>='0'&&input.charAt(index)<='7') {
                    index++;
                    while(input.charAt(index)>='0'&&input.charAt(index)<='7') {
                        index++;
                    }
                    result.add(new Result("INT8",input.substring(startIndex,index)));
                }
                else if(input.charAt(index)=='x') {
                    index++;
                    if((input.charAt(index)>='0'&&input.charAt(index)<='9')||(input.charAt(index)>='a'&&input.charAt(index)<='f')) {
                        index++;
                    }
                    while((input.charAt(index)>='0'&&input.charAt(index)<='9')||(input.charAt(index)>='a'&&input.charAt(index)<='f')) {
                        index++;
                    }
                    result.add(new Result("INT16",input.substring(startIndex,index)));
                }
                else {
                    result.add(new Result("INT10",input.substring(startIndex,index)));
                }
            }
            else if(input.charAt(index)=='+') {
                index++;
                result.add(new Result("+","-"));
            }
            else if(input.charAt(index)=='-') {
                index++;
                result.add(new Result("-","-"));
            }
            else if(input.charAt(index)=='*') {
                index++;
                result.add(new Result("*","-"));
            }
            else if(input.charAt(index)=='/') {
                index++;
                result.add(new Result("/","-"));
            }
            else if(input.charAt(index)=='<') {
                index++;
                result.add(new Result("<","-"));
            }
            else if(input.charAt(index)=='>') {
                index++;
                result.add(new Result(">","-"));
            }
            else if(input.charAt(index)=='(') {
                index++;
                result.add(new Result("(","-"));
            }
            else if(input.charAt(index)==')') {
                index++;
                result.add(new Result(")","-"));
            }
            else if(input.charAt(index)=='=') {
                index++;
                result.add(new Result("=","-"));
            }
            else if(input.charAt(index)==';') {
                index++;
                result.add(new Result(";","-"));
            }
            else {
                error();
                return result;
            }
        }
        return result;
    }
    public void error() {
        error = true;
        System.out.println("Input Error!");
    }
}