pnDetailMap.getOrDefault(pnCode, new ArrayList<>());
时间: 2024-04-28 09:23:41 浏览: 15
`pnDetailMap.getOrDefault(pnCode, new ArrayList<>())` 是一个 Map 的方法调用,它的作用是从 `pnDetailMap` 中获取 key 为 `pnCode` 的值,如果该 key 不存在,则返回一个空的 ArrayList。
具体来说,`pnDetailMap.getOrDefault(pnCode, new ArrayList<>())` 方法的参数是 `pnCode` 和一个默认值 `new ArrayList<>()`,它的返回值是 `pnDetailMap` 中 key 为 `pnCode` 的值,如果该值不存在,则返回一个空的 ArrayList。
在上面的代码中,我们将查询到的 `pnDetail` 列表保存在了 `pnDetailMap` 中,`pnDetailMap` 的 key 是 PN 编码,value 是对应的 `pnDetail` 列表。在组合 PN 和 `pnDetail` 列表时,我们需要从 `pnDetailMap` 中获取 key 为 PN 编码的 `pnDetail` 列表,如果该列表不存在,则返回一个空的列表。这就是 `pnDetailMap.getOrDefault(pnCode, new ArrayList<>())` 方法的作用。
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.