Java：使用 TreeSet
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/7776203/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Java: using TreeSet
提问by Belgi
I want to go over the objects inside my TreeSet, I can do it by making an array using toArraybut I don't need to go over all of the objects in the Set.
我想查看我的 中的对象TreeSet，我可以通过使用创建一个数组来完成，toArray但我不需要查看 Set 中的所有对象。
How can I go over the objects in the Set (starting with the first than the second etc') ?
如何查看 Set 中的对象（从第一个开始而不是第二个等）？
And another small question about TreeSet: Can I keep the objects in the TreeSetsorted (so the first object will be with the smallest key etc') ?
另一个小问题是TreeSet：我可以将对象保留在TreeSet排序中（因此第一个对象将具有最小的键等）？
edit: say I have a class myInt (with int myInteger) and I want to use it in TreeSet with a different oredering than the natural one, what do I need to define in my class (myInt) to do this ?
编辑：假设我有一个类 myInt（带有 int myInteger），并且我想在 TreeSet 中使用它与自然排序不同的排序，我需要在我的类（myInt）中定义什么来做到这一点？
回答by NPE
How can I go over the objects in the Set
如何查看 Set 中的对象
The easiest way to iterate over the items of the set is like so:
迭代集合的项目的最简单方法是这样的：
SortedSet<T> set = new TreeSet<T>();
for (T elem : set) {
// use elem
}
Can I keep the objects in the TreeSet sorted
我可以保持 TreeSet 中的对象排序吗
TreeSetis automatically sorted, so you don't need to do anything.
TreeSet会自动排序，因此您无需执行任何操作。
I have a class MyInt (with int myInteger) and I want to use it in TreeSet with a different ordering than the natural one
我有一个类 MyInt（带有 int myInteger），我想在 TreeSet 中使用它，它的顺序与自然顺序不同
You have two options:
您有两个选择：
Option 1: Make it implement Comparable<MyInt>:
选项 1：使其实施Comparable<MyInt>：
public class MyInt implements Comparable<MyInt> {
public int compareTo(MyInt o) {
// return -1 if `this` is less than `o`
// 0 if `this` is equal to `o`
// 1 of `this` is greater than `o`
}
}
Option 2: Supply a Comparator<MyInt>when constructing the TreeSet:
选项 2：Comparator<MyInt>在构建时提供一个TreeSet：
public class MyIntCmp implements Comparator<MyInt> {
// implement compare() and equals() as per Comparator javadoc
}
SortedSet<T> set = new TreeSet<T>(new MyIntCmp());
回答by MeBigFatGuy
for (MySetElementType element : mytreeset) {
}
TreeSet always keeps the objects sorted by how the objects compareTo (Comparable interface) is implemented. (Or you can pass a separate Comparator into the TreeSet constructor.)
TreeSet 始终按照对象 compareTo（Comparable 接口）的实现方式对对象进行排序。（或者您可以将单独的 Comparator 传递给 TreeSet 构造函数。）
回答by Android Killer
- The items inside TreeSet are automatically sorted according to their natural ordering if you are not giving your own comparator.
- Second thing you can define an Iterator to go through the TreeSet item directly without converting it to array.
- 如果您没有提供自己的比较器，则 TreeSet 中的项目会根据它们的自然顺序自动排序。
- 第二件事，您可以定义一个迭代器来直接遍历 TreeSet 项，而无需将其转换为数组。
回答by babsher
Since the SetTree implements iterable you can use a regular for each loop or use the iterator directly. In the javadocs it says that it will iterate in ascending order.
由于 SetTree 实现了 iterable，您可以为每个循环使用正则或直接使用迭代器。在 javadocs 中，它说它将按升序迭代。
http://download.oracle.com/javase/6/docs/api/java/util/TreeSet.html#iterator()
http://download.oracle.com/javase/6/docs/api/java/util/TreeSet.html#iterator()
