How to solve Java cyclic reference exception (CyclicReferenceException)

How to solve Java cyclic reference exception (CyclicReferenceException)

Summary:
In Java programming, circular reference is a common problem that may cause the program to Exceptions, one of the most common exceptions is CyclicReferenceException. This article will introduce the definition and causes of circular references, and provide some methods to solve circular reference exceptions, including using weak references, lazy initialization, etc.

Introduction:
In Java programming, mutual references between objects is a common phenomenon. When there are circular references between objects, it may cause program exceptions. One of the most common exceptions is CyclicReferenceException, which indicates that an ongoing operation caused an infinite cyclic reference.

1. Definition:
   Circular reference means that two or more objects refer to each other, forming a closed loop structure. If a program attempts to resolve such a circular reference, it will result in infinite recursion. In Java, circular references may occur in collection classes, nested classes, object associations, etc.
2. Cause:
   Circular references usually occur when developers are not careful, such as incorrect object association settings, elements in collection classes referencing each other, etc. For example, a parent object references a child object, and the child object references the parent object.
3. Solution:
   In order to solve the circular reference exception, we can take the following methods:

3.1 Use weak references:
Use weak references to avoid circular references memory leak problem. Weak reference means that when an object only has a weak reference, the garbage collector can still automatically recycle the object even if there is insufficient memory. In Java, you can use the WeakReference class to create weak references. Here is a sample code:

import java.lang.ref.WeakReference;

public class CyclicReferenceExample {
    private WeakReference<CyclicReferenceExample> reference;

    public void setReference(CyclicReferenceExample c) {
        reference = new WeakReference<>(c);
    }
    //...
}

In the above code, the instance of the referenced object is stored by using weak reference WeakReference. This way, even if there are circular references, the garbage collector can still reclaim them as long as there are no other strong references pointing to the objects.

3.2 Lazy initialization:
Another way to avoid circular references is lazy initialization. Lazy initialization means waiting until the referenced object is actually needed before initializing it. This avoids creating circular references between objects.

public class CyclicReferenceExample {
    private CyclicReferenceExample reference;

    public CyclicReferenceExample getReference() {
        if (reference == null) {
            reference = new CyclicReferenceExample();
        }
        return reference;
    }
    //...
}

In the above code, when the getReference() method is called, if the reference object has not been initialized, the initialization operation is performed. This can effectively avoid circular references.

Conclusion:
In Java programming, circular references are a common problem that may cause program exceptions. This article explains the definition and causes of circular references and provides two methods for solving circular reference exceptions: using weak references and lazy initialization. By adopting these methods, the circular reference problem can be effectively solved and the reliability and performance of the program can be improved.

Reference:

• WeakReference (Java Platform SE 8) – Oracle Help Center [https://docs.oracle.com/javase/8/docs/api/java/ lang/ref/WeakReference.html](https://docs.oracle.com/javase/8/docs/api/java/lang/ref/WeakReference.html)

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