TreeSet的排序comparable和Comparator - 黑马程序员技术交流社区

TreeSet的排序由comparable接口的compareTo方法返回的int值确定，0表示与根节点相同，不予存储；正数表示比根节点数据大，存在右节点；负数表示比根节点数据大，存在左节点package Set925.TreeSetDemo;public class Student implements Comparable<Student>{ private String name; private int 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; } public Student(String name, int age) {       this.name = name;       this.age = age; } public Student() { } @Override public int compareTo(Student o) {       int num=this.age-o.age;       int num2=num==0?this.getName().compareTo(o.getName()):num;       return num2; }}package Set925.TreeSetDemo;import java.util.TreeSet;public class TreeSetDemo { public static void main(String[] args) {       Student s1=new Student("王昭君",18);       Student s2=new Student("貂蝉",16);       Student s3=new Student("西施",17);       Student s4=new Student("杨玉环",20);       Student s5=new Student("小乔",18);       TreeSet<Student> ts=new TreeSet<>();       ts.add(s1);       ts.add(s2);       ts.add(s3);       ts.add(s4);       ts.add(s5);       for(Student s:ts){          System.out.println(s.getName()+s.getAge()+"岁");       } }}
比较器排序Comparator
package Set925.ComparatorDemo;public class Student { private String name; private int chinese; private int math; public String getName() {       return name; } public void setName(String name) {       this.name = name; } public int getChinese() {       return chinese; } public void setChinese(int chinese) {       this.chinese = chinese; } public int getMath() {       return math; } public void setMath(int math) {       this.math = math; } public Student(String name, int chinese, int math) {       this.name = name;       this.chinese = chinese;       this.math = math; } public Student() { } public int getSum(){       return chinese+math; }}
package Set925.ComparatorDemo;import java.util.Comparator;import java.util.TreeSet;public class Test { public static void main(String[] args) {       TreeSet<Student> ts=new TreeSet<>(new Comparator<Student>() {          @Override          public int compare(Student o1, Student o2) {             int num=o1.getSum()-o2.getSum();             int num2=num==0?o1.getName().compareTo(o2.getName()):num;             return num2;          }       });       Student s1=new Student("wangzhaojun",99,98);       Student s2=new Student("diaochan",98,99);       Student s3=new Student("xishi",95,96);       Student s4=new Student("yangyuhuan",100,97);       Student s5=new Student("xiaoqiao",96,99);       ts.add(s1);       ts.add(s2);       ts.add(s3);       ts.add(s4);       ts.add(s5);       for(Student s:ts){          System.out.println(s.getName()+":"+s.getChinese()+":"+s.getMath()+":"+s.getSum());       } }}
在TreeSet集合中熟练Comparable和Comparator方法。