4.6 简单的TreeSet示例

下面是一个简单的TreeSet的例子，通过这个简单的例子，你将了解：

• TreeSet是有序的
• 如何遍历一个TreeSet
• 如何检查空
• 如何删除一个元素

import java.util.Iterator;
import java.util.TreeSet;
 
public class TreeSetExample {
 
   public static void main(String[] args) {
    System.out.println("Tree Set Example!\n");
    TreeSet tree = new TreeSet();
    tree.add(12);
    tree.add(63);
    tree.add(34);
    tree.add(45);
 
    // here it test it's sorted, 63 is the last element. see output below
    Iterator iterator = tree.iterator();
    System.out.print("Tree set data: ");
 
    // Displaying the Tree set data
    while (iterator.hasNext()) {
        System.out.print(iterator.next() + " ");
    }
    System.out.println();
 
    // Check empty or not
    if (tree.isEmpty()) {
        System.out.print("Tree Set is empty.");
    } else {
        System.out.println("Tree Set size: " + tree.size());
    }
 
    // Retrieve first data from tree set
    System.out.println("First data: " + tree.first());
 
    // Retrieve last data from tree set
    System.out.println("Last data: " + tree.last());
 
    if (tree.remove(45)) { // remove element by value
        System.out.println("Data is removed from tree set");
    } else {
        System.out.println("Data doesn't exist!");
    }
    System.out.print("Now the tree set contain: ");
    iterator = tree.iterator();
 
    // Displaying the Tree set data
    while (iterator.hasNext()) {
        System.out.print(iterator.next() + " ");
    }
    System.out.println();
    System.out.println("Now the size of tree set: " + tree.size());
 
    // Remove all
    tree.clear();
    if (tree.isEmpty()) {
        System.out.print("Tree Set is empty.");
    } else {
        System.out.println("Tree Set size: " + tree.size());
    }
   }
}

输出：

Tree Set Example!

Tree set data: 12 34 45 63
Tree Set size: 4

First data: 12
Last data: 63

Data is removed from tree set

Now the tree set contain: 12 34 63
Now the size of tree set: 3

Tree Set is empty.