Stmt.java

import java.util.List;

public abstract class Stmt {
    public interface Visitor<R> {
        R visitBlockStmt(BlockStmt stmt);
        R visitExpressionStmt(ExpressionStmt stmt);
        R visitIfStmt(IfStmt stmt);
        R visitPrintStmt(PrintStmt stmt);
        R visitVarDeclareStmt(VarDeclareStmt stmt);
        R visitWhileStmt(WhileStmt stmt);
    }

    public abstract <R> R accept(Visitor<R> visitor);
}

class BlockStmt extends Stmt {
    public final List<Stmt> statements;

    public BlockStmt(List<Stmt> statements) {
        this.statements = statements;
    }

    @Override
    public <R> R accept(Visitor<R> visitor) {
        return visitor.visitBlockStmt(this);
    }
}

class ExpressionStmt extends Stmt {
    public final Expr expression;

    public ExpressionStmt(Expr expression) {
        this.expression = expression;
    }

    @Override
    public <R> R accept(Visitor<R> visitor) {
        return visitor.visitExpressionStmt(this);
    }
}

class IfStmt extends Stmt {
    public final Expr condition;
    public final Stmt thenBranch;
    public final Stmt elseBranch;

    public IfStmt(Expr condition, Stmt thenBranch, Stmt elseBranch) {
        this.condition = condition;
        this.thenBranch = thenBranch;
        this.elseBranch = elseBranch;
    }

    @Override
    public <R> R accept(Visitor<R> visitor) {
        return visitor.visitIfStmt(this);
    }
}

class PrintStmt extends Stmt {
    public final Expr expression;

    public PrintStmt(Expr expression) {
        this.expression = expression;
    }

    @Override
    public <R> R accept(Visitor<R> visitor) {
        return visitor.visitPrintStmt(this);
    }
}

class VarDeclareStmt extends Stmt {
    public final Token name;
    public final Expr initializer;

    public VarDeclareStmt(Token name, Expr initializer) {
        this.name = name;
        this.initializer = initializer;
    }

    @Override
    public <R> R accept(Visitor<R> visitor) {
        return visitor.visitVarDeclareStmt(this);
    }
}

class WhileStmt extends Stmt {
    public final Expr condition;
    public final Stmt body;

    public WhileStmt(Expr condition, Stmt body) {
        this.condition = condition;
        this.body = body;
    }

    @Override
    public <R> R accept(Visitor<R> visitor) {
        return visitor.visitWhileStmt(this);
    }
}