java学习之路-----集合（类集）-------set.pdf

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java学习之路-----集合(类集)-------set
分类: javase 2013-12-02 10:17 294人阅读评论(1) 收藏举报

               public class HashSetDemo {
 public static void main(String[] args) {
Set<String> set= new HashSet<String>();

( "A");
( "B");
( "C");
( "D");
( "E");
( "A");//重复添加
( "B");
( "F");

System. (set);

}
}
结果:
[D, E, F, A, B, C]
从结果中发现Hashset集合是不重复且无序的

public class TreeSetDemo {
public static void main(String[] args) {
Set<String>set= new TreeSet<String>();

( "C");
( "B");
( "A");
( "D");
( "E");
( "A");//重复添加
1
( "B");
( "F");

System. (set);
}
}
结果:
[A, B, C, D, E, F]

既然TreeSet可以排序,那么它可以对我们自己写的类型进行排序不?

class Person{
private String Name;

private int age ;
public String getName() {
return Name ;
}
public void setName(String name) {
Name = name;
}
public int getAge() {
return age ;
}
public void setAge(int age) {
= age;
}
public Person(String name, int age) {
Name = name;
= age;
}
2
}
public class TreeSetDemo1 {
public static void main(String[] args) {
Set<Person> set= new TreeSet<Person>();

( new Person("aaa" , 12));
( new Person("adc" , 12));
( new Person("abc" , 12));
( new Person("aac" , 12));
( new Person("aaa" , 13));

System. (set);
}
}
结果:
Exception in thread "main" :
cannot be cast to
at ( :1188)
at ( :531)
at ( :255)
at ( :41)
类转换错误
出现这个错误的原因是对于一个对象要想排序,必须要实现排序法则,
parable接口

class Person parable<Person>{