java - ArrayList通过List.of()初始化

Question

来自 Core Java for the Impatient:

... there is no initializer syntax for array lists. The best you can do is construct an array list like this:

ArrayList<String> friends =  new ArrayList<>(List.of("Peter", "Paul"));

但是当我尝试编译这段代码时出现错误:

error: cannot find symbol
                ArrayList<String> friends = new ArrayList<>(List.of("Peter", "Paul"));
                                                            ^
  symbol:   variable List

我的导入是:

import java.util.List;
import java.util.ArrayList;

谢谢

Answer 1

import java.util.ArrayList;
import java.util.List;

// ...
ArrayList<String> friends =  new ArrayList<>(List.of("Peter", "Paul"));

假设您至少运行 Java 9 就完全没问题。

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在 Java 9 之前，您需要使用 Arrays.asList() 而不是 List.of():

ArrayList<String> friends =  new ArrayList<>(Arrays.asList("Peter", "Paul"));