Java 自定义Sorted集合

From JavaSE6.0 编程指南

package wyf.jc;
import java.util.*;
//实现Comparable接口的元素类
class MyEntry implements Comparable
{
     //MyEntry的成员属性
     int size;
     //MyEntry类的无参构造器
     public MyEntry()
     {}
     //MyEntry类的有参构造器
     public MyEntry(int size)
     {
          this.size=size;
     }
     //实现compareTo方法
     public int compareTo(Object o)
     {
          //强制类型转换
          MyEntry me=(MyEntry)o;
          //定义排序的规则
          return this.size-me.size;
     }
     //重写equals方法
     public boolean equals(Object o)
     {
         //强制类型转换
        MyEntry me=(MyEntry)o;
        return (me.size==this.size);
     }
     //重写hashCode方法
     public int hashCode()
     {
         return 12;
     }
}
//主类
public class Sample14_12
{
     public static void main(String[] args)
     {
          //创建了一个TreeSet集合的对象
          TreeSet ts=new TreeSet();
          //向其中依次添加不同属性的学生对象
          System.out.println("=============插入21===============");
          ts.add(new MyEntry(21));
          System.out.println("=============插入19===============");
          ts.add(new MyEntry(19));
          System.out.println("=============插入18===============");
          ts.add(new MyEntry(18));
          System.out.println("=============插入28===============");
          ts.add(new MyEntry(28));
          System.out.println("=========再次插入21===============");
          ts.add(new MyEntry(21));
          System.out.println("==================================");
          //打印输出TreeSet中的内容
          System.out.print("这里是TreeSet操作后的结果：");
          System.out.println(ts);
     }
}

or：

package wyf.jc;
import java.util.*;
class Student implements Comparable
{
     //学生的成员属性
     String name;
     int age;
     int classNum;
     //学生类的无参构造器
     public Student(){}
     //学生类的有参构造器
     public Student(String name,int age,int classNum)
     {
          this.name=name;
          this.age=age;
          this.classNum=classNum;
     }
     //实现compareTo方法
     public int compareTo(Object o)
     {
          //强制类型转换
          Student s=(Student)o;
          //用classNum作为基准进行排序
          return this.classNum-s.classNum;
     }
}
//定义比较器
class AgeCompare implements Comparator
{
     public int compare(Object o1,Object o2)
     {
          //将接受到的对象的引用进行强制类型转换
          Student s1=(Student)o1;
          Student s2=(Student)o2;
          //指定按年龄进行排序
          return s1.age-s2.age;
     }
}
//主类
public class Sample14_13
{
     public static void main(String[] args)
     {
          //创建TreeSet对象ts1与ts2
          TreeSet ts1=new TreeSet();
          TreeSet ts2=new TreeSet(new AgeCompare());
          //向ts1中添加内容不同的学生对象的元素
          ts1.add(new Student("tom",21,97005));
          ts1.add(new Student("jerry",19,97003));
          ts1.add(new Student("lucy",18,97004));
          ts1.add(new Student("smith",28,97001));
          ts1.add(new Student("jc",23,97002));
          //想ts2中添加与ts1中相同的元素
          ts2.add(new Student("tom",21,97005));
          ts2.add(new Student("jerry",19,97003));
          ts2.add(new Student("lucy",18,97004));
          ts2.add(new Student("smith",28,97001));
          ts2.add(new Student("jc",23,97002));
          //打印ts1与ts2中的元素
          System.out.println("==========================="+
                                  "==========================");
          System.out.println("这里的SortedSet是按班号进行的排序：");
          System.out.println(ts1);
          System.out.println("==========================="+
                                  "==========================");
          System.out.println("这里的SortedSet是按年龄进行的排序：");
          System.out.println(ts2);
     }
}