TreeSet集合
2021/10/7 23:12:22
本文主要是介绍TreeSet集合,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
特点
- 不可以存储重复元素
- 没有索引
- 可以将元素按照指定规则进行排序
自然排序Comparable的使用
- 要求按照年龄从小到大排序,年龄相同时,按照姓名的字母顺序排序
package com.ding.mytreeset; /** * @Description TODO * @Author 丁帅帅 * @Date 21/10/07 22:25 * @Version 1.0 */ public class Student implements Comparable<Student>{ private String name; private int age; public Student(String name, int age) { this.name = name; this.age = age; } public Student() { } 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; } @Override public String toString() { return "Student{" + "name='" + name + '\'' + ", age=" + age + '}'; } public int compareTo(Student o) { //按照对象的年龄进行排序 //主要判断条件 //this是当前对象,o是已存在的对象 //小的放左边 int result = this.age - o.age; //次要判断条件 result = result == 0 ? this.name.compareTo(o.getName()) : result; return result; } }
package com.ding.mytreeset; import java.util.TreeSet; /** * @Description TreeSet集合来存储Student类型 * @Author 丁帅帅 * @Date 21/10/07 22:24 * @Version 1.0 */ public class MyTreeSet { public static void main(String[] args) { TreeSet<Student> ts = new TreeSet<Student>(); Student s1 = new Student("aa",28); Student s2 = new Student("lisi",27); Student s3 = new Student("wangwu",29); Student s4 = new Student("bb",28); Student s5 = new Student("qianqi",30); ts.add(s1); ts.add(s2); ts.add(s3); ts.add(s4); ts.add(s5); System.out.println(ts); } }
结果
[Student{name='lisi', age=27}, Student{name='aa', age=28}, Student{name='bb', age=28}, Student{name='wangwu', age=29}, Student{name='qianqi', age=30}]
比较器排序Comparator的使用
- 要求: 按照年龄从小到大排序,年龄相同时,按照姓名的字母顺序排序
package com.ding.mytreeset; /** * @Description TODO * @Author 丁帅帅 * @Date 21/10/07 22:42 * @Version 1.0 */ public class Teacher { private String name; private int age; public Teacher() { } public Teacher(String name, int age) { this.name = name; this.age = age; } 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; } @Override public String toString() { return "Teacher{" + "name='" + name + '\'' + ", age=" + age + '}'; } }
package com.ding.mytreeset; import java.util.Comparator; import java.util.TreeSet; /** * @Description TODO * @Author 丁帅帅 * @Date 21/10/07 22:42 * @Version 1.0 */ public class MyTreeSetTeacher { public static void main(String[] args) { TreeSet<Teacher> ts = new TreeSet<Teacher>(new Comparator<Teacher>() { public int compare(Teacher o1, Teacher o2) { //o1表示现在要存入的那个元素 //o2表示已经存入到集合中的元素 //主要条件 int result = o1.getAge() - o2.getAge(); //次要条件 result = result == 0 ? o1.getName().compareTo(o2.getName()) :result; return result; } }); Teacher t1 = new Teacher("zhangsan",23); Teacher t2 = new Teacher("lisi",22); Teacher t3 = new Teacher("aa",24); Teacher t4 = new Teacher("bb",24); ts.add(t1); ts.add(t2); ts.add(t3); ts.add(t4); System.out.println(ts); } }
结果
[Teacher{name='lisi', age=22}, Teacher{name='zhangsan', age=23}, Teacher{name='aa', age=24}, Teacher{name='bb', age=24}]
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