会合框架-TreeSet

/*TreeSet ;元素是有序的,但是不可以元素重复.                    */import java.util.*;class TreeSetDemo{    public static void main(String [] args)    {        TreeSet ts = new TreeSet();                ts.add("java01");        ts.add("java03");        ts.add("java02");        ts.add("java04");        ts.add("java04");                Iterator it = ts.iterator();                while(it.hasNext())        {            sop(it.next());        }                ts.remove("java02");        sop(ts);            }    public static void sop(Object obj)    {        System.out.println(obj);    }        }class Student{    private String name;    private int age;        Student(String name,int age)    {        this.name = name;        this.age = age;    }        public String getName()    {        return name;    }    public int getAge()    {        return age;    }}

/*        TreeSet存储自定义对象                (会抛出类型转换异常ClassCastException) Student类无法转成Comparable.        因此Student类需要实现Comparable接口.并且覆写compareTo方法.排序的方式为自然顺序.                排序时,当主要条件相同时,还要判断一下次要条件.                        需求: 按学生的年龄排序.*/import java.util.*;class TreeSetTest{    public static void main(String [] args)    {        TreeSet ts = new TreeSet();                ts.add(new Student("lisi08",19));        ts.add(new Student("lisi02",22));        ts.add(new Student("lisi007",20));        ts.add(new Student("lisi09",19));                        Iterator it = ts.iterator();                while(it.hasNext())        {            Student stu = (Student)it.next();            sop(stu.getName()+"------"+stu.getAge());        }            }    public static void sop(Object obj)    {        System.out.println(obj);    }    }class Student implements Comparable //该接口强制让学生具备了比较性. (实现了该接口需要覆盖其compareTo方法){    private String name;    private int age;        Student(String name,int age)    {        this.name = name;        this.age = age;    }    public int compareTo(Object obj)    {                //return 1; //怎么存的怎么取出        //return -1;  //倒取存入的对象        //return 0;        //只会存入第一个存入的对象.                if(!(obj instanceof Student))            throw new RuntimeException("不是学生对象");                    Student s = (Student)obj;                System.out.println(this.name+"---compareTo---"+s.name);                if(this.age>s.age)            return 1;        if(this.age==s.age)        {            return this.name.compareTo(s.name);        }        return -1;            }                public String getName()    {        return name;    }    public int getAge()    {        return age;    }}

/*让容器自身具备比较性,定义一个比较器.将比较器对象传递给TreeSet集合的构造函数;思路步骤:定义一个容器让这个容器实现comparator,并且覆写其中的compare方法.*/import java.util.*;class TreeSetTest2{    public static void main(String [] args)    {        //TreeSet ts = new TreeSet(); //传入的不是比较器对象时,调用的是CompareTo方法.                TreeSet ts = new TreeSet(new MyComparator());  //将比较器传递给TreeSet的构造函数.                ts.add(new Student("lisi08",19));        ts.add(new Student("lisi02",22));        ts.add(new Student("lisi02",23));        ts.add(new Student("lisi007",20));        ts.add(new Student("lisi09",19));                Iterator it = ts.iterator();                while(it.hasNext())        {            Student stu = (Student)it.next();            sop(stu.getName()+"-----"+stu.getAge());        }                    }        public static void sop(Object obj)    {        System.out.println(obj);    }        }class Student implements Comparable //让学生类具备了比较性{    private String name;    private int age;    Student(String name,int age)    {        this.name = name;        this.age = age;    }    public String getName()    {        return name;    }    public int getAge()    {        return age;    }        public int compareTo(Object obj)  //覆写了Comparable中的compareTo方法.    {        if(!(obj instanceof Student))            throw new RuntimeException("bushixueshengduixiang");                Student s = (Student)obj;        if(this.age>s.age)            return 1;        if(this.age==s.age)        {            return this.name.compareTo(s.name);        }        return -1;    }}class MyComparator implements Comparator  //定义一个容器并实现了Comparator接口{    public int compare(Object o1,Object o2)  //覆写其中的compare方法.    {                if(!(o1 instanceof Student ||o2 instanceof Student))            throw new RuntimeException("对象错误.");                Student s1 = (Student)o1;        Student s2 = (Student)o2;                //return s1.getName().compareTo(s2.getName()); //无法存储到姓名相同年龄不同的对象.                int num = s1.getName().compareTo(s2.getName());  //判断返回值 (1 0 -1)        if(num==0)   //判断的名字相同时,在判断其年龄是否相同.        {            return s1.getAge()-s2.getAge();            /*            if(s1.getAge()>s2.getAge())                return 1;            if(s1.getAge()==s2.getAge())                return 0;            return -1;            */        }                return num;            }}

/*练习:按照字符串长度排序*/import java.util.*;class TreeSetExam{    public static void main(String [] args)    {        TreeSet ts = new TreeSet(new StrLengthCompare());                    ts.add("abcd");        ts.add("cc");        ts.add("cba");        ts.add("a");        ts.add("hahaha");        ts.add("aa");                Iterator it = ts.iterator();                while(it.hasNext())        {            sop(it.next());        }            }        public static void sop(Object obj)    {        System.out.println(obj);    }    }class StrLengthCompare implements Comparator{    public int compare(Object o1,Object o2)    {        if(!(o1 instanceof String || o2 instanceof String))            throw new RuntimeException("ERROR");                String s1 = (String)o1;        String s2 = (String)o2;                //int num = s1.length()-s2.length();        int num = new Integer(s1.length()).compareTo(new Integer(s2.length()));                if(num==0) //判断长度一样的字符串的自然排序.        {            return s1.compareTo(s2);        }        return num;    }}