Treeset（自然顺序的实现）

/**
 * 存学员成绩
 * TreeSet
 * 问题：java.lang.ClassCastException: com.qf.treeset.test.Student cannot be cast to java.lang.Comparable异常
 * 解决方法：给自定义类添加比较器，有的类系统已自动实现了Comparable接口，这里只针对于自定义类
 * 比较器：
 *    内部比较器
 *       自定义类添加比较器
 *          1.自定义类   实现 java.lang.Comparable;
 *          2.实现 int compareTo(T o) 方法 比较此对象与比较对象的顺序      制定比较规则
 *       匿名内部类 
 *          1.实例一个集合的时候（） new Comparator<T o> 接口
 *          2.实现 int compare(T o1,T o2) 方法 比较用来排序的两个参数    制定比较规则
 *          
 *    外部比较器
 *       定义一个类  实现比较方法
 *       1.自定义一个类   实现    Comparator<T o> 接口
 *       2.实现 int compare(T o1,T o2) 方法 比较用来排序的两个参数    制定比较规则
 * 
 *

 */

1.内部类实现Comparable

public class Worker implements Comparable<Worker>{public String name;public int age;public double salary;public Worker() {super();}public Worker(String name, int age, double salary) {super();this.name = name;this.age = age;this.salary = salary;}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 double getSalary() {return salary;}public void setSalary(double salary) {this.salary = salary;}@Overridepublic int compareTo(Worker w) {// TODO Auto-generated method stub/* * 自定义排序规则 *  * */int num1 = -this.name.compareTo(w.getName());//姓名降序int num2 = (this.age - w.getAge());//姓名相同，年龄升序int num3 = -((Double)this.salary).compareTo(w.getSalary());//姓名年龄相同，薪水降序return num1==0?num2==0?num3:num2:num1;}}

public class Test {public static void main(String[] args) {// TODO Auto-generated method stubTreeSet<Worker> t = new TreeSet<Worker>();Worker w1 = new Worker("zhang3", 18, 3000);Worker w2 = new Worker("zhang3", 19, 3000);Worker w3 = new Worker("li4", 25, 3500);Worker w4= new Worker("li4", 25, 3600);Worker w5 = new Worker("wang5", 22, 3200);t.add(w1);t.add(w2);t.add(w3);t.add(w4);t.add(w5);System.out.println("姓名\t年龄\t薪水");for(Worker w : t){System.out.println(w.getName()+"\t"+w.getAge()+"\t"+w.getSalary());}}}

输出结果：

姓名 年龄 薪水
zhang3 18 3000.0
zhang3 19 3000.0
wang5 22 3200.0
li4         253600.0
li4         253500.0

2.匿名内部类实现接口方法

public class Worker2{public String name;public int age;public double salary;public Worker2() {super();}public Worker2(String name, int age, double salary) {super();this.name = name;this.age = age;this.salary = salary;}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 double getSalary() {return salary;}public void setSalary(double salary) {this.salary = salary;}}

public class Test2 {public static void main(String[] args) {// TODO Auto-generated method stubTreeSet<Worker2> t = new TreeSet<Worker2>(new Comparator<Worker2>() {@Overridepublic int compare(Worker2 o1, Worker2 o2) {/* * 自定义排序规则 *  * */int num1 = -o1.getName().compareTo(o2.getName());//姓名降序int num2 = (o1.getAge() - o2.getAge());//姓名相同，年龄升序int num3 = -((Double)o1.getSalary()).compareTo(o2.getSalary());//姓名年龄相同，薪水降序return num1==0?num2==0?num3:num2:num1;}});Worker2 w1 = new Worker2("zhang3", 18, 3000);Worker2 w2 = new Worker2("zhang3", 19, 3000);Worker2 w3 = new Worker2("li4", 25, 3500);Worker2 w4 = new Worker2("li4", 25, 3600);Worker2 w5 = new Worker2("wang5", 22, 3200);t.add(w1);t.add(w2);t.add(w3);t.add(w4);t.add(w5);System.out.println("姓名\t年龄\t薪水");for (Worker2 w : t) {System.out.println(w.getName() + "\t" + w.getAge() + "\t" + w.getSalary());}}}

输出结果：

姓名 年龄 薪水
zhang3 18 3000.0
zhang3 19 3000.0
wang5 22 3200.0
li4         253600.0
li4         253500.0

3.外部类实现Comparator<T o> 接口

public class WorkerComparable implements Comparator<Worker2> {@Overridepublic int compare(Worker2 o1, Worker2 o2) {// TODO Auto-generated method stub/* * 自定义排序规则 *  * */int num1 = -o1.getName().compareTo(o2.getName());//姓名降序int num2 = (o1.getAge() - o2.getAge());//姓名相同，年龄升序int num3 = -((Double)o1.getSalary()).compareTo(o2.getSalary());//姓名年龄相同，薪水降序return num1==0?num2==0?num3:num2:num1;}}

public class Test3 {public static void main(String[] args) {// TODO Auto-generated method stubComparator<Worker2> wc = new WorkerComparable();TreeSet<Worker2> t = new TreeSet<Worker2>(wc);Worker2 w1 = new Worker2("zhang3", 18, 3000);Worker2 w2 = new Worker2("zhang3", 19, 3000);Worker2 w3 = new Worker2("li4", 25, 3500);Worker2 w4= new Worker2("li4", 25, 3600);Worker2 w5 = new Worker2("wang5", 22, 3200);t.add(w1);t.add(w2);t.add(w3);t.add(w4);t.add(w5);System.out.println("姓名\t年龄\t薪水");for(Worker2 w : t){System.out.println(w.getName()+"\t"+w.getAge()+"\t"+w.getSalary());}}}

输出结果：

姓名 年龄 薪水
zhang3 18 3000.0
zhang3 19 3000.0
wang5 22 3200.0
li4         253600.0
li4         253500.0