用java写一个语法分析器
时间: 2023-05-20 16:04:04 浏览: 53
好的,我可以为您提供一个基本的Java语法分析器的代码示例。请注意,这只是一个简单的示例,您可能需要根据您的具体需求进行修改和调整。
```
import java.util.*;
public class SyntaxAnalyzer {
private List<String> tokens;
private int currentToken;
public SyntaxAnalyzer(List<String> tokens) {
this.tokens = tokens;
this.currentToken = 0;
}
public void parse() {
program();
if (currentToken != tokens.size()) {
throw new RuntimeException("Unexpected token: " + tokens.get(currentToken));
}
}
private void program() {
statementList();
}
private void statementList() {
statement();
while (currentToken < tokens.size() && tokens.get(currentToken).equals(";")) {
currentToken++;
statement();
}
}
private void statement() {
if (tokens.get(currentToken).equals("if")) {
ifStatement();
} else if (tokens.get(currentToken).equals("while")) {
whileStatement();
} else if (tokens.get(currentToken).equals("print")) {
printStatement();
} else {
throw new RuntimeException("Unexpected token: " + tokens.get(currentToken));
}
}
private void ifStatement() {
currentToken++; // consume "if"
expression();
if (!tokens.get(currentToken).equals("then")) {
throw new RuntimeException("Expected 'then', but found: " + tokens.get(currentToken));
}
currentToken++; // consume "then"
statementList();
if (tokens.get(currentToken).equals("else")) {
currentToken++; // consume "else"
statementList();
}
if (!tokens.get(currentToken).equals("endif")) {
throw new RuntimeException("Expected 'endif', but found: " + tokens.get(currentToken));
}
currentToken++; // consume "endif"
}
private void whileStatement() {
currentToken++; // consume "while"
expression();
if (!tokens.get(currentToken).equals("do")) {
throw new RuntimeException("Expected 'do', but found: " + tokens.get(currentToken));
}
currentToken++; // consume "do"
statementList();
if (!tokens.get(currentToken).equals("endwhile")) {
throw new RuntimeException("Expected 'endwhile', but found: " + tokens.get(currentToken));
}
currentToken++; // consume "endwhile"
}
private void printStatement() {
currentToken++; // consume "print"
expression();
}
private void expression() {
term();
while (currentToken < tokens.size() && (tokens.get(currentToken).equals("+") || tokens.get(currentToken).equals("-"))) {
currentToken++;
term();
}
}
private void term() {
factor();
while (currentToken < tokens.size() && (tokens.get(currentToken).equals("*") || tokens.get(currentToken).equals("/"))) {
currentToken++;
factor();
}
}
private void factor() {
if (tokens.get(currentToken).equals("(")) {
currentToken++; // consume "("
expression();
if (!tokens.get(currentToken).equals(")")) {
throw new RuntimeException("Expected ')', but found: " + tokens.get(currentToken));
}
currentToken++; // consume ")"
} else if (tokens.get(currentToken).equals("number")) {
currentToken++; // consume "number"
} else {
throw new RuntimeException("Unexpected token: " + tokens.get(currentToken));
}
}
}
```
这是一个简单的语法分析器,它可以解析基本的算术表达式,包括加、减、乘、除和括号。您可以将您的代码作为输入传递给它,然后它将检查您的代码是否符合语法规则。