课本235页2-3题

package org.hanqi.array;

import java.util.*;

public class Xiti2 {

    public static void main(String[] args) {
        List<String> list=new ArrayList<String>();
        list.add("A");
        list.add("a");
        list.add("c");
        list.add("C");
        list.add("a");
        for(String s:list)
        {
            System.out.println(s);
        }
        System.out.println("集合长度="+list.size());
        System.out.println("List集合成功添加");
        
        
        HashSet<String>s1=new HashSet<String>();
        s1.add("A");
        s1.add("a");
        s1.add("c");
        s1.add("C");
        s1.add("a");
        for(String t:s1)
        {
            System.out.println(t);
        }
        System.out.println("集合长度="+s1.size());
        System.out.println("Set集合不能成功添加");

    }

}

第三题

package org.hanqi.array;

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

public class Emp {

    private String key;
    private String value;
    public Emp(String key,String value)
    {
        this.key=key;
        this.value=value;
    }
    public String getKey() {
        return key;
    }
    public void setKey(String key) {
        this.key = key;
    }
    public String getValue() {
        return value;
    }
    public void setValue(String value) {
        this.value = value;
    }
    public static void main(String[] args)
    {
        Map<String, String>m=new HashMap<String, String>();
        Emp emp=new Emp("001","德州扒鸡");
        Emp emp2=new Emp("002","北京烤鸭");
        Emp emp3=new Emp("003","绝味鸭头");
        Emp emp4=new Emp("004","博山酥锅");
        Emp emp5=new Emp("005","武汉热干面");
        Emp emp6=new Emp("006","周村烧饼");
        Emp emp7=new Emp("007","淄博烧烤");
        
        
        m.put(emp.getKey(), emp.getValue());
        m.put(emp2.getKey(), emp2.getValue());
        m.put(emp3.getKey(), emp3.getValue());
        m.put(emp4.getKey(), emp4.getValue());
        m.put(emp5.getKey(), emp5.getValue());
        m.put(emp6.getKey(), emp6.getValue());
        m.put(emp7.getKey(), emp7.getValue());
        
        m.remove(emp5);
        for(String t:m.keySet())
        {
            if(t=="005")
            {
                m.remove(emp5);
            }
            else
            {
                System.out.println(t);
            }
        }
    }

}