Java-set集合

package exception;

import  java.util.Map;
import java.util.TreeMap;
import  java.util.HashMap;

public class TestMap {

    public static void main(String[] args) {
        //map

        Map<String,String> m1 = new HashMap<>();

        //添加数据
        //key不能重复
        m1.put("0531","济南");
        m1.put("0532","青岛");
        m1.put("0533","淄博");
        m1.put("","章丘");  //如果key重复，那么新的value覆盖旧的value

        //长度
        System.out.println(m1.size());

        //获取数据
        System.out.println(m1.get("0531"));

        //移除
        m1.remove("0532");
        System.out.println(m1.size());

        System.out.println("key是否存在="+m1.containsKey("0533"));

        System.out.println(m1.get(m1.keySet()));

        //遍历
        //通过遍历key的set集合，同事获取value
        for(String k:m1.keySet())
        {
            System.out.println(m1.get(k));
        }

        //TreeMap
        TreeMap<Integer,Person> tm =new TreeMap<>();

        tm.put(100, new Person("X",20));
        tm.put(110, new Person("Y",23));
        tm.put(104, new Person("Z",20));
        tm.put(102, new Person("W",21));

        //遍历
        for(Integer k:tm.keySet())
        {
            System.out.println("ke="+k+"value"+tm.get(k));
        }

    }

}

package exception;

import java.util.Set;
import java.util.HashSet;
import java.util.Iterator;

public class Test04 {

    public static void main(String[] args){ 

    //set集合
    //实现类HashSet 哈希Hash
    //搜索引擎，利用哈希值
    //不能存放重复数据
    //没有顺序和索引
    Set<Person> s1=new HashSet<>();

    Person p0=new Person("A",20);
    Person p1=new Person("b",20);
    Person p2=new Person("c",20);

    //不能存放重复数据，也不报错
    s1.add(p0);
    s1.add(p1);
    s1.add(p2);

    s1.add(new Person("B",30));

    System.out.println(s1.size());

    System.out.println(s1.contains(p0));

    s1.remove(p0);

    System.out.println(s1.size());

    System.out.println(s1.contains(p0));

    for(Person a:s1)
    {
        System.out.println(a);
    }

    //迭代器
    Iterator<Person> it = s1.iterator();
    //
    while(it.hasNext())
    {
        Person p = it.next();
        System.out.println(p);
    }
    }    

}

package exception;

import java.util.Set;
import java.util.TreeSet;
import java.util.HashSet;
import java.util.Iterator;

public class Test04 {

    public static void main(String[] args){ 

    //set集合
    //实现类HashSet 哈希Hash
    //搜索引擎，利用哈希值
    //不能存放重复数据
    //没有顺序和索引
    Set<Person> s1=new HashSet<>();

    Person p0=new Person("A",20);
    Person p1=new Person("b",20);
    Person p2=new Person("c",20);

    //不能存放重复数据，也不报错
    s1.add(p0);
    s1.add(p1);
    s1.add(p2);

    s1.add(new Person("B",30));

    System.out.println(s1.size());

    System.out.println(s1.contains(p0));

    s1.remove(p0);

    System.out.println(s1.size());

    System.out.println(s1.contains(p0));

    for(Person a:s1)
    {
        System.out.println(a);
    }

    //迭代器
    Iterator<Person> it = s1.iterator();
    //
    while(it.hasNext())
    {
        Person p = it.next();
        System.out.println(p);
    }

    //TreeSet
    TreeSet<String> ts= new TreeSet<>();

    ts.add("Z");
    ts.add("X");
    ts.add("B");
    ts.add("C");
    ts.add("Y");
    ts.add("W");
    ts.add("M");
    ts.add("A");
    //ts.addAll(null);

    for(String str:ts)
    {
        System.out.println(str);
    }
}
}