Collections.singletonList和Lists.newArrayList有什么区别

Collections.singletonList是Java集合框架中的一个方法，它返回一个不可修改的List，该List只包含指定对象的单个元素。而Lists.newArrayList是Guava库中的一个方法，它返回一个可修改的ArrayList，其中包含指定元素的所有元素。它们的主要区别在于返回的List对象是否可修改。

如果您需要创建只包含一个元素的不可修改列表，则可以使用Collections.singletonList。如果您需要创建一个可修改列表，则可以使用Lists.newArrayList。

需要注意的是，由于Collections.singletonList返回的列表不可修改，因此在尝试修改它时，会抛出UnsupportedOperationException异常。而Lists.newArrayList返回的列表是可修改的，可以通过add、remove等方法来修改列表中的元素。

相关问题

apache Lists.newArrayList<>()

This code creates a new ArrayList instance using the generic type parameter `<E>` provided by the `List` interface in the Apache Commons Collections library. The `newArrayList<>()` method initializes the ArrayList with an initial capacity of 10. This method is useful when you want to create a new ArrayList instance and populate it with elements in a single step. For example:

List<String> myList = Lists.newArrayList("apple", "banana", "orange");

This creates a new ArrayList of Strings and populates it with the elements "apple", "banana", and "orange".

apache Lists.newArrayList<>() pom

This is a code snippet from the Apache Commons Collections library.

`Lists.newArrayList<>()` is a method call that creates a new ArrayList that can hold any type of object. The angle brackets (`<>`) indicate that the ArrayList is a generic type, meaning that it can hold any type of object, but the type must be specified when the list is initialized.

The `pom` part of the code is not related to the `Lists.newArrayList<>()` method call. It is likely referring to the Maven Project Object Model (POM) file, which is an XML file that contains information about a project and its dependencies. The `pom` file is used by Maven to build and manage the project.