java编程之集合框架

            在写哈弗曼编码时，看到了优先队列，可是不会用，就用数组排序代替了。现在弄明白了，写出来，希望对读者有所帮助。

            优先队列的使用需要实现Comparator接口，具体代码如下：

package learning_lev1_集合框架;

import java.util.Comparator;
import java.util.PriorityQueue;

public class Pq {
	public void testPriQueue(){
		
		//使用匿名内部类实现comparator接口，匿名类的对象为comp
		Comparator<Student> comp=new Comparator<Student>() {
			//实现接口里面的方法，选择age作为比较大小的对象
			public int compare(Student o1, Student o2) {
				Student stu1=o1;
				Student stu2=o2;
				if(stu1.getAge()>stu2.getAge())return 1;
				else if(stu1.getAge()<stu2.getAge())return -1;
				else return 0;
			}
		};
		
		//比较器的对象作为优先队列的参数，才能实现优先队列每次按要求取得最大最小值
		PriorityQueue<Student> queue=new PriorityQueue(1,comp);
		
		Student stu1=new Student("唐僧", 30, 01);
		Student stu2=new Student("悟空",32,02);
		Student stu3=new Student("八戒", 34,03);
		Student stu4=new Student(" 沙僧 ",31,04);
		queue.add(stu2);
		queue.add(stu1);
		queue.add(stu4);
		queue.add(stu3);
		
		//peek（）与poll（）的区别是，调用peek（）后，队列中的元素
		//个数不变，而调用poll（）后，最大或最小键值元素被去除
		Student student=queue.peek();
		//Student student=queue.poll();
		System.out.println(queue.size());
		System.out.println(student);
		
	}
	public static void main(String[] args) {
		new Pq().testPriQueue();
	}

}

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package learning_lev1_集合框架;

public class Student {
	private int num;
	private String name;
	private int age;
	public int getNum() {
		return num;
	}
	public void setNum(int num) {
		this.num = num;
	}

	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	
	public Student(String name, int age,int num) {
		this.name = name;
		this.age = age;
		this.num=num;
	}
	
	public String toString(){
		return "编号"+num+",姓名："+name+",年龄："+age;
	}
	
}