Java 调用toString方法时发生堆栈溢出错误

这是我的代码，但当我执行程序时，我会出现很多错误，我不知道为什么。有人能帮我吗

RegisteredUser.java

public class RegisteredUser {
    private String nickname;
    ArrayList<ReviewDAO> reviews;

    public RegisteredUser(String nickname) {
        this.nickname = nickname;
        reviews = new ArrayList<>();
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public void addReview(ReviewDAO review) {
        if (!this.reviews.contains(review)) {
            this.reviews.add(review);
            review.addRegisteredUser(this);
        }
    }

    @Override
    public String toString() {
        return "RegisteredUser{" +
                "nickname='" + nickname + '\'' +
                ", reviews=" + reviews +
                '}';
    }
}

public abstract class ReviewDAO {
    RegisteredUser registeredUser;

    public abstract boolean write(Review review);

    public void addRegisteredUser(RegisteredUser registeredUser) {
        this.registeredUser = registeredUser;
    }

    @Override
    public String toString() {
        return "ReviewDAO{" +
                "registeredUser=" + registeredUser +
                '}';
    }
}

public class Review {
    private String title;
    private String description;
    private int rank;
    private boolean isAnonymous;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public int getRank() {
        return rank;
    }

    public void setRank(int rank) {
        this.rank = rank;
    }

    public boolean isAnonymous() {
        return isAnonymous;
    }

    public void setAnonymous(boolean anonymous) {
        isAnonymous = anonymous;
    }
}

public class ReviewDAO_MongoDB extends ReviewDAO {
    @Override
    public boolean write(Review review) {
        return false;
        // todo
    }
}

public class ReviewDAO_Factory {

    public ReviewDAO getReviewDAO(String technology) throws ExecutionControl.NotImplementedException {
        if (technology.equals("mongodb"))
            return new ReviewDAO_MongoDB();
        else
            throw new ExecutionControl.NotImplementedException("");
    }
}

public class BusinessLogic {
    public static void main(String[] args) throws ExecutionControl.NotImplementedException {
        ReviewDAO_Factory reviewDAO_factory = new ReviewDAO_Factory();
        RegisteredUser registeredUser = new RegisteredUser("Alessandro");

        registeredUser.addReview(reviewDAO_factory.getReviewDAO("mongodb"));
        System.out.println(registeredUser.toString());
    }
}

Review.java

public class RegisteredUser {
    private String nickname;
    ArrayList<ReviewDAO> reviews;

    public RegisteredUser(String nickname) {
        this.nickname = nickname;
        reviews = new ArrayList<>();
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public void addReview(ReviewDAO review) {
        if (!this.reviews.contains(review)) {
            this.reviews.add(review);
            review.addRegisteredUser(this);
        }
    }

    @Override
    public String toString() {
        return "RegisteredUser{" +
                "nickname='" + nickname + '\'' +
                ", reviews=" + reviews +
                '}';
    }
}

public abstract class ReviewDAO {
    RegisteredUser registeredUser;

    public abstract boolean write(Review review);

    public void addRegisteredUser(RegisteredUser registeredUser) {
        this.registeredUser = registeredUser;
    }

    @Override
    public String toString() {
        return "ReviewDAO{" +
                "registeredUser=" + registeredUser +
                '}';
    }
}

public class Review {
    private String title;
    private String description;
    private int rank;
    private boolean isAnonymous;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public int getRank() {
        return rank;
    }

    public void setRank(int rank) {
        this.rank = rank;
    }

    public boolean isAnonymous() {
        return isAnonymous;
    }

    public void setAnonymous(boolean anonymous) {
        isAnonymous = anonymous;
    }
}

public class ReviewDAO_MongoDB extends ReviewDAO {
    @Override
    public boolean write(Review review) {
        return false;
        // todo
    }
}

public class ReviewDAO_Factory {

    public ReviewDAO getReviewDAO(String technology) throws ExecutionControl.NotImplementedException {
        if (technology.equals("mongodb"))
            return new ReviewDAO_MongoDB();
        else
            throw new ExecutionControl.NotImplementedException("");
    }
}

public class BusinessLogic {
    public static void main(String[] args) throws ExecutionControl.NotImplementedException {
        ReviewDAO_Factory reviewDAO_factory = new ReviewDAO_Factory();
        RegisteredUser registeredUser = new RegisteredUser("Alessandro");

        registeredUser.addReview(reviewDAO_factory.getReviewDAO("mongodb"));
        System.out.println(registeredUser.toString());
    }
}

查看wao\u MongoDB.java

public class RegisteredUser {
    private String nickname;
    ArrayList<ReviewDAO> reviews;

    public RegisteredUser(String nickname) {
        this.nickname = nickname;
        reviews = new ArrayList<>();
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public void addReview(ReviewDAO review) {
        if (!this.reviews.contains(review)) {
            this.reviews.add(review);
            review.addRegisteredUser(this);
        }
    }

    @Override
    public String toString() {
        return "RegisteredUser{" +
                "nickname='" + nickname + '\'' +
                ", reviews=" + reviews +
                '}';
    }
}

public abstract class ReviewDAO {
    RegisteredUser registeredUser;

    public abstract boolean write(Review review);

    public void addRegisteredUser(RegisteredUser registeredUser) {
        this.registeredUser = registeredUser;
    }

    @Override
    public String toString() {
        return "ReviewDAO{" +
                "registeredUser=" + registeredUser +
                '}';
    }
}

public class Review {
    private String title;
    private String description;
    private int rank;
    private boolean isAnonymous;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public int getRank() {
        return rank;
    }

    public void setRank(int rank) {
        this.rank = rank;
    }

    public boolean isAnonymous() {
        return isAnonymous;
    }

    public void setAnonymous(boolean anonymous) {
        isAnonymous = anonymous;
    }
}

public class ReviewDAO_MongoDB extends ReviewDAO {
    @Override
    public boolean write(Review review) {
        return false;
        // todo
    }
}

public class ReviewDAO_Factory {

    public ReviewDAO getReviewDAO(String technology) throws ExecutionControl.NotImplementedException {
        if (technology.equals("mongodb"))
            return new ReviewDAO_MongoDB();
        else
            throw new ExecutionControl.NotImplementedException("");
    }
}

public class BusinessLogic {
    public static void main(String[] args) throws ExecutionControl.NotImplementedException {
        ReviewDAO_Factory reviewDAO_factory = new ReviewDAO_Factory();
        RegisteredUser registeredUser = new RegisteredUser("Alessandro");

        registeredUser.addReview(reviewDAO_factory.getReviewDAO("mongodb"));
        System.out.println(registeredUser.toString());
    }
}

查看Dao_Factory.java

public class RegisteredUser {
    private String nickname;
    ArrayList<ReviewDAO> reviews;

    public RegisteredUser(String nickname) {
        this.nickname = nickname;
        reviews = new ArrayList<>();
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public void addReview(ReviewDAO review) {
        if (!this.reviews.contains(review)) {
            this.reviews.add(review);
            review.addRegisteredUser(this);
        }
    }

    @Override
    public String toString() {
        return "RegisteredUser{" +
                "nickname='" + nickname + '\'' +
                ", reviews=" + reviews +
                '}';
    }
}

public abstract class ReviewDAO {
    RegisteredUser registeredUser;

    public abstract boolean write(Review review);

    public void addRegisteredUser(RegisteredUser registeredUser) {
        this.registeredUser = registeredUser;
    }

    @Override
    public String toString() {
        return "ReviewDAO{" +
                "registeredUser=" + registeredUser +
                '}';
    }
}

public class Review {
    private String title;
    private String description;
    private int rank;
    private boolean isAnonymous;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public int getRank() {
        return rank;
    }

    public void setRank(int rank) {
        this.rank = rank;
    }

    public boolean isAnonymous() {
        return isAnonymous;
    }

    public void setAnonymous(boolean anonymous) {
        isAnonymous = anonymous;
    }
}

public class ReviewDAO_MongoDB extends ReviewDAO {
    @Override
    public boolean write(Review review) {
        return false;
        // todo
    }
}

public class ReviewDAO_Factory {

    public ReviewDAO getReviewDAO(String technology) throws ExecutionControl.NotImplementedException {
        if (technology.equals("mongodb"))
            return new ReviewDAO_MongoDB();
        else
            throw new ExecutionControl.NotImplementedException("");
    }
}

public class BusinessLogic {
    public static void main(String[] args) throws ExecutionControl.NotImplementedException {
        ReviewDAO_Factory reviewDAO_factory = new ReviewDAO_Factory();
        RegisteredUser registeredUser = new RegisteredUser("Alessandro");

        registeredUser.addReview(reviewDAO_factory.getReviewDAO("mongodb"));
        System.out.println(registeredUser.toString());
    }
}

BusinessLogic.java

public class RegisteredUser {
    private String nickname;
    ArrayList<ReviewDAO> reviews;

    public RegisteredUser(String nickname) {
        this.nickname = nickname;
        reviews = new ArrayList<>();
    }

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public void addReview(ReviewDAO review) {
        if (!this.reviews.contains(review)) {
            this.reviews.add(review);
            review.addRegisteredUser(this);
        }
    }

    @Override
    public String toString() {
        return "RegisteredUser{" +
                "nickname='" + nickname + '\'' +
                ", reviews=" + reviews +
                '}';
    }
}

public abstract class ReviewDAO {
    RegisteredUser registeredUser;

    public abstract boolean write(Review review);

    public void addRegisteredUser(RegisteredUser registeredUser) {
        this.registeredUser = registeredUser;
    }

    @Override
    public String toString() {
        return "ReviewDAO{" +
                "registeredUser=" + registeredUser +
                '}';
    }
}

public class Review {
    private String title;
    private String description;
    private int rank;
    private boolean isAnonymous;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public int getRank() {
        return rank;
    }

    public void setRank(int rank) {
        this.rank = rank;
    }

    public boolean isAnonymous() {
        return isAnonymous;
    }

    public void setAnonymous(boolean anonymous) {
        isAnonymous = anonymous;
    }
}

public class ReviewDAO_MongoDB extends ReviewDAO {
    @Override
    public boolean write(Review review) {
        return false;
        // todo
    }
}

public class ReviewDAO_Factory {

    public ReviewDAO getReviewDAO(String technology) throws ExecutionControl.NotImplementedException {
        if (technology.equals("mongodb"))
            return new ReviewDAO_MongoDB();
        else
            throw new ExecutionControl.NotImplementedException("");
    }
}

public class BusinessLogic {
    public static void main(String[] args) throws ExecutionControl.NotImplementedException {
        ReviewDAO_Factory reviewDAO_factory = new ReviewDAO_Factory();
        RegisteredUser registeredUser = new RegisteredUser("Alessandro");

        registeredUser.addReview(reviewDAO_factory.getReviewDAO("mongodb"));
        System.out.println(registeredUser.toString());
    }
}

我越来越

线程“main”java.lang.StackOverflowerr中出现异常 在RegisteredUser.toString（RegisteredUser.java:33） 位于java.base/java.lang.String.valueOf（String.java:2951） 在ReviewDAO.toString（ReviewDAO.java:15）

进程已完成，退出代码为1

---

错误首先，这个设计看起来有缺陷。你不应该把POJO和DAO混在一起。DAO是处理POJO上CRUD操作的“数据访问对象”类。这里有2个POJO-查看和注册用户。ReviewDAO负责对Review的托管/非托管实例（或实体）执行CRUD操作。 对于RegisteredUser，您可能还需要另一个POJO（在实际代码中）

其次，我看到您正在调用List contains方法来检查用户是否已经进行了审查，但是您还没有在ReviewDAO中实现“equals”和“hashCode”

public void addReview(ReviewDAO review) {
        if (!this.reviews.contains(review)) {
            this.reviews.add(review);
            review.addRegisteredUser(this);
        }
    }

我做了一些调整。请检查它是否满足您的需要：

RegisteredUser类（已使用哈希集，因为“包含”搜索将更快）

复习课：

业务逻辑类

---

在

RegisteredUser.toString（）

中，您正在打印每个

ReviewDAO

然后打印出

RegisteredUser

然后打印每个

ReviewDAO

然后…@Seelenvirtuose如何解决此错误？这里讨论了类似的情况：。父项>子项>父项。。。无限循环。这能回答你的问题吗@同样的错误。。。如果我的代码是错误的，而不仅仅是被重写的toString（）方法呢？如果我没有在Review.java中重写equals和hash呢？为什么我的设计有问题？包含检查的内容将不正确。只有当两个对象引用相同时（在JVM内存中），它才会返回true。我只根据它们的标题比较了两个评论。您也可以在比较时添加其他字段，如描述。为什么我的设计有问题？RegisteredUser实体不应与ReviewDAO关联，而应与Review关联？