使用Java语言编写PL/0编译程序的语法分析程序

以下是使用Java语言编写的PL/0编译程序的语法分析程序：

import java.util.ArrayList;
import java.util.List;
import java.util.Stack;

public class Parser {

    private Lexer lexer;
    private Token currentToken;
    private Stack<Integer> jumpStack;
    private int codePointer;
    private List<Instruction> instructions;

    public Parser(Lexer lexer) {
        this.lexer = lexer;
        this.currentToken = lexer.getNextToken();
        this.jumpStack = new Stack<>();
        this.codePointer = 0;
        this.instructions = new ArrayList<>();
    }

    public List<Instruction> parse() {
        program();
        return instructions;
    }

    private void program() {
        block();
        match(TokenType.PERIOD);
    }

    private void block() {
        if (currentToken.getType() == TokenType.CONST) {
            constDeclaration();
        }
        if (currentToken.getType() == TokenType.VAR) {
            varDeclaration();
        }
        while (currentToken.getType() == TokenType.PROCEDURE) {
            procedureDeclaration();
        }
        statement();
    }

    private void constDeclaration() {
        match(TokenType.CONST);
        do {
            String name = currentToken.getValue();
            match(TokenType.IDENTIFIER);
            match(TokenType.EQUAL);
            int value = Integer.parseInt(currentToken.getValue());
            match(TokenType.NUMBER);
            instructions.add(new Instruction(Operation.LIT, value));
            instructions.add(new Instruction(Operation.STO, SymbolTable.addSymbol(name)));
        } while (currentToken.getType() == TokenType.COMMA);
        match(TokenType.SEMICOLON);
    }

    private void varDeclaration() {
        match(TokenType.VAR);
        do {
            String name = currentToken.getValue();
            match(TokenType.IDENTIFIER);
            instructions.add(new Instruction(Operation.INT, SymbolTable.addSymbol(name)));
        } while (currentToken.getType() == TokenType.COMMA);
        match(TokenType.SEMICOLON);
    }

    private void procedureDeclaration() {
        match(TokenType.PROCEDURE);
        String name = currentToken.getValue();
        match(TokenType.IDENTIFIER);
        match(TokenType.SEMICOLON);
        int procedurePointer = codePointer;
        instructions.add(null);
        block();
        instructions.add(new Instruction(Operation.RET, 0));
        instructions.set(procedurePointer, new Instruction(Operation.JMP, codePointer));
        SymbolTable.addSymbol(name, procedurePointer);
        match(TokenType.SEMICOLON);
    }

    private void statement() {
        if (currentToken.getType() == TokenType.IDENTIFIER) {
            String name = currentToken.getValue();
            match(TokenType.IDENTIFIER);
            if (currentToken.getType() == TokenType.ASSIGN) {
                match(TokenType.ASSIGN);
                expression();
                instructions.add(new Instruction(Operation.STO, SymbolTable.getSymbol(name)));
            } else {
                callStatement(name);
            }
        } else if (currentToken.getType() == TokenType.BEGIN) {
            match(TokenType.BEGIN);
            statement();
            while (currentToken.getType() == TokenType.SEMICOLON) {
                match(TokenType.SEMICOLON);
                statement();
            }
            match(TokenType.END);
        } else if (currentToken.getType() == TokenType.IF) {
            match(TokenType.IF);
            condition();
            match(TokenType.THEN);
            int falseJumpPointer = instructions.size();
            instructions.add(null);
            statement();
            if (currentToken.getType() == TokenType.ELSE) {
                match(TokenType.ELSE);
                int endJumpPointer = instructions.size();
                instructions.add(null);
                instructions.set(falseJumpPointer, new Instruction(Operation.JPF, codePointer));
                statement();
                instructions.set(endJumpPointer, new Instruction(Operation.JMP, codePointer));
            } else {
                instructions.set(falseJumpPointer, new Instruction(Operation.JPF, codePointer));
            }
        } else if (currentToken.getType() == TokenType.WHILE) {
            match(TokenType.WHILE);
            int loopStartPointer = codePointer;
            condition();
            match(TokenType.DO);
            int falseJumpPointer = instructions.size();
            instructions.add(null);
            statement();
            instructions.add(new Instruction(Operation.JMP, loopStartPointer));
            instructions.set(falseJumpPointer, new Instruction(Operation.JPF, codePointer));
        } else if (currentToken.getType() == TokenType.CALL) {
            match(TokenType.CALL);
            String name = currentToken.getValue();
            match(TokenType.IDENTIFIER);
            callStatement(name);
        } else if (currentToken.getType() == TokenType.READ) {
            match(TokenType.READ);
            String name = currentToken.getValue();
            match(TokenType.IDENTIFIER);
            instructions.add(new Instruction(Operation.RED, SymbolTable.getSymbol(name)));
        } else if (currentToken.getType() == TokenType.WRITE) {
            match(TokenType.WRITE);
            expression();
            instructions.add(new Instruction(Operation.WRT, 0));
        }
    }

    private void expression() {
        TokenType operator = currentToken.getType();
        if (operator == TokenType.PLUS || operator == TokenType.MINUS) {
            match(operator);
        }
        term();
        while (currentToken.getType() == TokenType.PLUS || currentToken.getType() == TokenType.MINUS) {
            operator = currentToken.getType();
            match(operator);
            term();
            if (operator == TokenType.PLUS) {
                instructions.add(new Instruction(Operation.ADD, 0));
            } else {
                instructions.add(new Instruction(Operation.SUB, 0));
            }
        }
    }

    private void term() {
        factor();
        while (currentToken.getType() == TokenType.TIMES || currentToken.getType() == TokenType.DIVIDE) {
            TokenType operator = currentToken.getType();
            match(operator);
            factor();
            if (operator == TokenType.TIMES) {
                instructions.add(new Instruction(Operation.MUL, 0));
            } else {
                instructions.add(new Instruction(Operation.DIV, 0));
            }
        }
    }

    private void factor() {
        if (currentToken.getType() == TokenType.NUMBER) {
            int value = Integer.parseInt(currentToken.getValue());
            match(TokenType.NUMBER);
            instructions.add(new Instruction(Operation.LIT, value));
        } else if (currentToken.getType() == TokenType.IDENTIFIER) {
            String name = currentToken.getValue();
            match(TokenType.IDENTIFIER);
            instructions.add(new Instruction(Operation.LOD, SymbolTable.getSymbol(name)));
        } else if (currentToken.getType() == TokenType.LPAREN) {
            match(TokenType.LPAREN);
            expression();
            match(TokenType.RPAREN);
        } else {
            throw new RuntimeException("Invalid factor: " + currentToken.getValue());
        }
    }

    private void condition() {
        if (currentToken.getType() == TokenType.ODD) {
            match(TokenType.ODD);
            expression();
            instructions.add(new Instruction(Operation.ODD, 0));
        } else {
            expression();
            TokenType operator = currentToken.getType();
            relationalOperator();
            expression();
            if (operator == TokenType.EQUAL) {
                instructions.add(new Instruction(Operation.EQL, 0));
            } else if (operator == TokenType.NOT_EQUAL) {
                instructions.add(new Instruction(Operation.NEQ, 0));
            } else if (operator == TokenType.LESS_THAN) {
                instructions.add(new Instruction(Operation.LES, 0));
            } else if (operator == TokenType.LESS_THAN_OR_EQUAL) {
                instructions.add(new Instruction(Operation.LEQ, 0));
            } else if (operator == TokenType.GREATER_THAN) {
                instructions.add(new Instruction(Operation.GTR, 0));
            } else if (operator == TokenType.GREATER_THAN_OR_EQUAL) {
                instructions.add(new Instruction(Operation.GEQ, 0));
            }
        }
    }

    private void relationalOperator() {
        TokenType operator = currentToken.getType();
        if (operator == TokenType.EQUAL || operator == TokenType.NOT_EQUAL ||
                operator == TokenType.LESS_THAN || operator == TokenType.LESS_THAN_OR_EQUAL ||
                operator == TokenType.GREATER_THAN || operator == TokenType.GREATER_THAN_OR_EQUAL) {
            match(operator);
        } else {
            throw new RuntimeException("Invalid relational operator: " + currentToken.getValue());
        }
    }

    private void callStatement(String name) {
        instructions.add(new Instruction(Operation.CAL, SymbolTable.getSymbol(name)));
    }

    private void match(TokenType expectedType) {
        if (currentToken.getType() == expectedType) {
            currentToken = lexer.getNextToken();
        } else {
            throw new RuntimeException("Invalid token: " + currentToken.getValue() +
                    ". Expected " + expectedType.toString());
        }
    }
}

此程序使用递归下降方法进行语法分析，并将生成的指令保存在一个列表中。其中包括各种声明（常量、变量和过程）、语句（赋值、条件、循环、调用、读入和输出）和表达式（加减乘除和关系运算）。在处理过程中，还要维护符号表和跳转指令的位置。