请用java实现LR(0)分析表的构造及测试例子

好的，下面是LR(0)分析表的构造及测试例子的Java代码：

import java.util.*;

public class LR0Parser {
    private List<String[]> productions;
    private Map<String, Set<String>> firstSets;
    private Map<String, Set<String>> followSets;
    private Map<String, Map<String, String>> actionTable;
    private Map<String, Map<String, Integer>> gotoTable;
    private String startSymbol;

    public LR0Parser(List<String[]> productions, String startSymbol) {
        this.productions = productions;
        this.startSymbol = startSymbol;
        this.firstSets = computeFirstSets();
        this.followSets = computeFollowSets();
        this.actionTable = computeActionTable();
        this.gotoTable = computeGotoTable();
    }

    public boolean parse(List<String> input) {
        Stack<String> stack = new Stack<>();
        stack.push("0");
        int inputIndex = 0;

        while (!stack.isEmpty()) {
            String state = stack.peek();
            String symbol = inputIndex < input.size() ? input.get(inputIndex) : "$";
            String action = actionTable.get(state).getOrDefault(symbol, "");

            if (action.isEmpty()) {
                return false;
            } else if (action.startsWith("s")) {
                int nextState = Integer.parseInt(action.substring(1));
                stack.push(symbol);
                stack.push(Integer.toString(nextState));
                inputIndex++;
            } else if (action.startsWith("r")) {
                int productionIndex = Integer.parseInt(action.substring(1));
                String[] production = productions.get(productionIndex);
                int numSymbolsToRemove = production[1].split("\\s+").length;

                for (int i = 0; i < numSymbolsToRemove * 2; i++) {
                    stack.pop();
                }

                String prevState = stack.peek();
                String nonterminal = production[0];
                int nextState = gotoTable.get(prevState).get(nonterminal);
                stack.push(nonterminal);
                stack.push(Integer.toString(nextState));
            } else if (action.equals("acc")) {
                return true;
            }
        }

        return false;
    }

    private Map<String, Set<String>> computeFirstSets() {
        Map<String, Set<String>> firstSets = new HashMap<>();

        for (String[] production : productions) {
            String nonterminal = production[0];

            if (!firstSets.containsKey(nonterminal)) {
                firstSets.put(nonterminal, new HashSet<>());
            }
        }

        boolean changed;

        do {
            changed = false;

            for (String[] production : productions) {
                String nonterminal = production[0];
                String[] symbols = production[1].split("\\s+");

                for (String symbol : symbols) {
                    if (symbol.equals("epsilon")) {
                        changed |= firstSets.get(nonterminal).add("epsilon");
                        break;
                    } else if (isTerminal(symbol)) {
                        changed |= firstSets.get(nonterminal).add(symbol);
                        break;
                    } else {
                        Set<String> symbolFirstSet = firstSets.get(symbol);

                        for (String symbolFirst : symbolFirstSet) {
                            if (!symbolFirst.equals("epsilon")) {
                                changed |= firstSets.get(nonterminal).add(symbolFirst);
                            }
                        }

                        if (!symbolFirstSet.contains("epsilon")) {
                            break;
                        }
                    }
                }
            }
        } while (changed);

        return firstSets;
    }

    private Map<String, Set<String>> computeFollowSets() {
        Map<String, Set<String>> followSets = new HashMap<>();

        for (String[] production : productions) {
            String nonterminal = production[0];

            if (!followSets.containsKey(nonterminal)) {
                followSets.put(nonterminal, new HashSet<>());
            }
        }

        followSets.get(startSymbol).add("$");

        boolean changed;

        do {
            changed = false;

            for (String[] production : productions) {
                String nonterminal = production[0];
                String[] symbols = production[1].split("\\s+");

                for (int i = 0; i < symbols.length; i++) {
                    String symbol = symbols[i];

                    if (isNonterminal(symbol)) {
                        Set<String> symbolFirstSet = firstSets.get(symbol);

                        for (String symbolFirst : symbolFirstSet) {
                            if (!symbolFirst.equals("epsilon")) {
                                changed |= followSets.get(symbol).add(symbolFirst);
                            }
                        }

                        if (symbolFirstSet.contains("epsilon") || i == symbols.length - 1) {
                            Set<String> nonterminalFollowSet = followSets.get(nonterminal);

                            for (String nonterminalFollow : nonterminalFollowSet) {
                                changed |= followSets.get(symbol).add(nonterminalFollow);
                            }
                        }
                    }
                }
            }
        } while (changed);

        return followSets;
    }

    private Map<String, Map<String, String>> computeActionTable() {
        Map<String, Map<String, String>> actionTable = new HashMap<>();

        for (int i = 0; i < productions.size(); i++) {
            String[] production = productions.get(i);
            String nonterminal = production[0];
            String[] symbols = production[1].split("\\s+");
            Set<String> followSet = followSets.get(nonterminal);

            for (String symbol : followSet) {
                if (!actionTable.containsKey(Integer.toString(i))) {
                    actionTable.put(Integer.toString(i), new HashMap<>());
                }

                actionTable.get(Integer.toString(i)).put(symbol, "r" + i);
            }
        }

        for (int i = 0; i < productions.size(); i++) {
            String[] production = productions.get(i);
            String[] symbols = production[1].split("\\s+");

            for (int j = 0; j < symbols.length; j++) {
                String symbol = symbols[j];

                if (isNonterminal(symbol)) {
                    int nextState = findNextState(i, symbol);

                    if (!actionTable.containsKey(Integer.toString(i))) {
                        actionTable.put(Integer.toString(i), new HashMap<>());
                    }

                    if (actionTable.get(Integer.toString(i)).containsKey(symbol)) {
                        if (!actionTable.get(Integer.toString(i)).get(symbol).equals("s" + nextState)) {
                            throw new RuntimeException("Reduce/shift conflict detected.");
                        }
                    } else {
                        actionTable.get(Integer.toString(i)).put(symbol, "s" + nextState);
                    }
                } else if (isTerminal(symbol)) {
                    int nextState = findNextState(i, symbol);

                    if (!actionTable.containsKey(Integer.toString(i))) {
                        actionTable.put(Integer.toString(i), new HashMap<>());
                    }

                    if (actionTable.get(Integer.toString(i)).containsKey(symbol)) {
                        if (!actionTable.get(Integer.toString(i)).get(symbol).equals("s" + nextState)) {
                            throw new RuntimeException("Reduce/shift conflict detected.");
                        }
                    } else {
                        actionTable.get(Integer.toString(i)).put(symbol, "s" + nextState);
                    }
                }
            }
        }

        for (int i = 0; i < productions.size(); i++) {
            if (!actionTable.containsKey(Integer.toString(i))) {
                actionTable.put(Integer.toString(i), new HashMap<>());
            }

            if (productions.get(i)[0].equals(startSymbol)) {
                actionTable.get(Integer.toString(i)).put("$", "acc");
            }
        }

        return actionTable;
    }

    private Map<String, Map<String, Integer>> computeGotoTable() {
        Map<String, Map<String, Integer>> gotoTable = new HashMap<>();

        for (int i = 0; i < productions.size(); i++) {
            String[] production = productions.get(i);
            String[] symbols = production[1].split("\\s+");

            for (int j = 0; j < symbols.length; j++) {
                String symbol = symbols[j];

                if (isNonterminal(symbol)) {
                    int nextState = findNextState(i, symbol);

                    if (!gotoTable.containsKey(Integer.toString(i))) {
                        gotoTable.put(Integer.toString(i), new HashMap<>());
                    }

                    gotoTable.get(Integer.toString(i)).put(symbol, nextState);
                }
            }
        }

        return gotoTable;
    }

    private int findNextState(int state, String symbol) {
        for (int i = state + 1; i < productions.size(); i++) {
            String[] production = productions.get(i);

            if (production[0].equals(symbol)) {
                return i;
            }
        }

        return -1;
    }

    private boolean isTerminal(String symbol) {
        return !isNonterminal(symbol);
    }

    private boolean isNonterminal(String symbol) {
        return symbol.matches("[A-Z].*");
    }
}

下面是一个测试例子，假设我们有以下文法：

S -> E
E -> E + T
E -> E - T
E -> T
T -> T * F
T -> T / F
T -> F
F -> ( E )
F -> id

我们可以使用以下代码来测试：

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<String[]> productions = new ArrayList<>();
        productions.add(new String[] { "S", "E" });
        productions.add(new String[] { "E", "E + T" });
        productions.add(new String[] { "E", "E - T" });
        productions.add(new String[] { "E", "T" });
        productions.add(new String[] { "T", "T * F" });
        productions.add(new String[] { "T", "T / F" });
        productions.add(new String[] { "T", "F" });
        productions.add(new String[] { "F", "( E )" });
        productions.add(new String[] { "F", "id" });

        LR0Parser parser = new LR0Parser(productions, "S");
        List<String> input = Arrays.asList("id", "+", "id", "*", "id", "$");

        if (parser.parse(input)) {
            System.out.println("Accepted");
        } else {
            System.out.println("Rejected");
        }
    }
}

这个测试例子中，我们使用了一个包含加减乘除和括号的简单的表达式，用来测试LR(0)分析表的构造和使用。