java中的Set集合TreeSet集合
1、自然排序：
/*
* 需求：自定义对象自然排序(按年龄从小到大)且对象唯一！
* */
public class TreeSetTest {
public static void main(String[] args) {
TreeSet<Student> ts = new TreeSet<Student>();
Student s1 = new Student("one",1);
Student s2 = new Student("two",2);
Student s3 = new Student("three",3);
Student s4 = new Student("four",4);
Student s5 = new Student("five",5);
Student s6 = new Student("six",6);
Student s7 = new Student("six",6);
Student s8 = new Student("four",4);
ts.add(s1);
ts.add(s2);
ts.add(s3);
ts.add(s4);
ts.add(s5);
ts.add(s6);
ts.add(s7);
ts.add(s8);
for(Student s :ts)
{
System.out.println(s.getAge() + s.getName());
}
}
}
2、因为底层是用了comparable的comparetor方法！所以学生类要实现comparable并重写comparable方法：
public class Student implements Comparable<Student>
public int compareTo(Student o) {
//按年龄进行排序：
int num = this.age - o.age;
//去掉重复！
if(num == 0)
{
this.name.compareTo(o.name);
}
return num;
}
3、控制台打印结果：
1one
2two
3three
4four
5five
6six
4、比较器排序：
public class CompareDemo {
public static void main(String[] args) {
TreeSet<Student> ts = new TreeSet<Student>(
//这里用匿名内部类：内部类的格式是new 一个类或者接口然后重写方法就好了！
new Comparator<Student>() {
public int compare(Student o1, Student o2) {
int num = o1.getAge() - o2.getAge();
if(num == 0)
{
o1.getName().compareTo(o2.getName());
}
return num;
};
}
);
Student s1 = new Student("one",1);
Student s2 = new Student("two",2);
Student s3 = new Student("three",3);
Student s4 = new Student("four",4);
Student s5 = new Student("five",5);
Student s6 = new Student("six",6);
Student s7 = new Student("six",6);
Student s8 = new Student("four",4);
ts.add(s1);
ts.add(s2);
ts.add(s3);
ts.add(s4);
ts.add(s5);
ts.add(s6);
ts.add(s7);
ts.add(s8);
for(Student s :ts)
{
System.out.println(s.getAge() + s.getName());
}
}
}