如何获取某个属性的值列表(How can I get a list of values for a certain property)

如何获取某个属性的值列表(How can I get a list of values for a certain property)

我想在ArrayList有一个对象的某个属性的值列表。 假设我有这样一个类：

public class Foo { private String b, a, r; //Constructor... //Getters... }

然后我创建一个ArrayList<Foo> ：

ArrayList<Foo> fooList = new ArrayList<>(); fooList.add(new Foo("How", "Hey", "Hey")); fooList.add(new Foo("Can", "Hey", "Hey")); fooList.add(new Foo("I", "Hey", "Hey")); fooList.add(new Foo("Get", "Hey", "Hey")); fooList.add(new Foo("Those?", "Hey", "Hey"));

在ArrayList<Foo> ，是否可以获取Foo的某个属性的List而不必使用for循环迭代我的ArrayList ？ 在Objective-c中，也许某些东西与valueforkey相似 。 如果我有一个包含How ， Can ， I ， Get和Those的ArrayList<String> ，这将使用TextUtils.join()更容易打印值。

I'd like to have a list of values for a certain property of an object inside an ArrayList. Supposing I have a class like this:

public class Foo { private String b, a, r; //Constructor... //Getters... }

Then I create an ArrayList<Foo>:

ArrayList<Foo> fooList = new ArrayList<>(); fooList.add(new Foo("How", "Hey", "Hey")); fooList.add(new Foo("Can", "Hey", "Hey")); fooList.add(new Foo("I", "Hey", "Hey")); fooList.add(new Foo("Get", "Hey", "Hey")); fooList.add(new Foo("Those?", "Hey", "Hey"));

In an ArrayList<Foo>, is it possible to get a List of a certain property of Foo without having to iterate over my ArrayList using a for loop? Maybe something simillar to valueforkey in Objective-c. This would make easier to print values using TextUtils.join() if I had an ArrayList<String> containing How, Can, I, Get, and Those.

最满意答案

使用Java 8，您可以流式传输，映射和收集：

List<String> list = fooList.stream() .map(Foo::getProp) .collect(Collectors.toList());

如果您有Guava，您可以像这样获得列表的转换视图：

List<String> list = Lists.transform(fooList, Foo::getProp);

Java 7版本：

List<String> list = Lists.transform(fooList, new Function<Foo, String>() { @Override public String apply(Foo foo) { return foo.getProp(); } });

Using Java 8, you can stream, map and collect:

List<String> list = fooList.stream() .map(Foo::getProp) .collect(Collectors.toList());

If you have Guava, you can get a transformed view of your list like this:

List<String> list = Lists.transform(fooList, Foo::getProp);

The Java 7 version:

List<String> list = Lists.transform(fooList, new Function<Foo, String>() { @Override public String apply(Foo foo) { return foo.getProp(); } });