Advantages and disadvantages of immutable objects in Java?

Advantages of immutable objects: thread-safe, low memory consumption, easy to reason, cacheable, comparable and hashable. Disadvantages: Unmodifiable, low efficiency, may cause memory leaks. Practical cases: String, Integer, BigDecimal, Collections.unmodifiableList(). Applicable scenarios: When thread safety, low memory consumption, cacheability, and ease of reasoning and comparison are required.

Advantages and Disadvantages of Immutable Objects in Java

What are immutable objects?

An immutable object is an object whose internal state cannot be modified. Once created, the field values ​​of an immutable object do not change.

Advantages:

• Thread safety: Immutable objects are thread-safe because their state will not be accessed concurrently Change.
• Low memory consumption: Immutable objects can be shared because their copies have the same state. This saves memory.
• Easier to reason: Since the state of an immutable object does not change, it is easier to understand and reason about its behavior.
• Cacheable: Immutable objects can be cached because they do not change, thus improving performance.
• Comparability and Hashability: Immutable objects can be easily compared and hashed because their field values ​​never change.

Disadvantages:

• Immutable: Immutable objects cannot modify their state after they are created. This can be troublesome when objects need to be updated dynamically.
• Inefficiency: For objects whose state needs to be updated frequently, immutable objects may cause inefficiency because new objects must be created to change the state.
• Memory Leak: If an immutable object stores references to other mutable objects, it may cause a memory leak.

Practical cases

The following are some practical cases of immutable objects in Java:

• String: String The class is immutable, which means it cannot be modified once created.
• Integer: Integer classes (and other primitive wrapper classes) are immutable, meaning that they represent values ​​that do not change.
• BigDecimal: BigDecimal class is immutable and used for precise arithmetic operations.
• Collections.unmodifiableList(): This method returns an immutable view of the given list.

When to use immutable objects?

Immutable objects should be used when you need the following features:

• Thread safety
• Low memory consumption
• Can Cacheability
• Easy to reason about and compare

Avoid using immutable objects when you need to be able to dynamically update the object.

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