The difference between addall and add in java

Difference: 1. addAll() receives a collection parameter, add() receives a single element parameter; 2. addAll() adds multiple elements at a time, add() adds one element at a time; 3. add() returns Boolean value, addAll() has no return value; 4. addAll() is only applicable to collections that implement the Collection interface; 5. addAll() is more efficient when adding elements in batches. Scenario selection: Use addAll() when there are a large number of elements; use addAll() when the collection type supports addAll(); use addAll() when performance is critical and there are a large number of elements.

The difference between addAll() and add() in Java

addAll() and add() are two important methods in the Java collection class, both of which can be used to add elements to the collection. The following are the differences between them:

1. Parameter type

• add() method receives a single element as a parameter.
• addAll() The method receives another collection as a parameter.

2. Add the number of elements

• add() method can only add one element to the collection.
• addAll() method can add multiple elements to the collection at one time.

3. Return value

• add() method returns a Boolean value indicating whether the element has been successfully added to in collection.
• addAll() The method does not return any value.

4. Collection type

• add() method can be used in any type of collection (such as ArrayList, HashSet) used on. The
• addAll() method can only be used on collections that implement the Collection interface.

5. Performance

• If you need to add a large number of elements at once, the addAll() method is usually better than add () method is more efficient.

Scenario Selection

According to the above differences, choosing add() or addAll() depends on the following Factor:

• Number of elements: If you need to add multiple elements, please use addAll().
• Collection type: Make sure that the collection used supports the addAll() method.
• Performance: If performance is critical, use addAll() when you need to add a large number of elements at once.

Example

<code class="java">// 使用 add() 添加单个元素
List<String> names = new ArrayList<>();
names.add("John");

// 使用 addAll() 添加多个元素
List<String> newNames = new ArrayList<>();
newNames.addAll(List.of("Jane", "Mary", "Tom"));</code>

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