1. 如何遍历 Map 的 Key 集，value 集， key-value 集，使用上泛型
Map<String,Integer> map = new HashMap<String,Integer>();
map.put(); ....
//遍历key
Set<String> keySet = map.keySet();
for(String key : keySet){
	System.out.println(key);
}

//遍历value
Collection<Integer> values =  map.values();
Iterator<Integer> iterator = values.iterator():
while(iterator.hasNext()){
	System.out.println(iterator.next());
}

//遍历key-value
Set<Map.Entry<String,Integer>> entrySet = map.entrySet();
Iterator<Map.Entry<String,Integer>> iterator = entrySet.iterator();
while(iterator.hasNext()){
	Map.Entry<String,Integer> entry = iterator.next();
	String key = entry.getkey();
	Integer value = entry.getValue();
	System.out.println(key + "--->" + value);
}
2. 写出使用Iterator 和 增强for循环遍历List<String>的代码，使用上泛型

3. 提供一个方法，用于遍历获取HashMap<String,String>中的所有value，并存放在List中返回。考虑上集合中泛型的使用。
public List<String> getValueList(HashMap<String,String> map){
	ArrayList<String> valueList = new ArrayList<>();
	Collcetion<String> values = map.values();
	for(String value ： values){
		valueList.add(value);
	}
	return valueList;	
}


4. 创建一个与a.txt文件同目录下的另外一个文件b.txt
File file1 = new File("d:\\a\\a.txt");
File file2 = new File(file1.getParent(),"b.txt");

5. Map接口中的常用方法有哪些
增：put(K k, V v)
删：V remove(K k)
改：put(K k, V v)
查：V get(K k)
长度：int size()
遍历：keySet()，values()，entrySet()

package top.qaqaq.java.P581;

import org.junit.jupiter.api.Test;

import java.io.File;
import java.io.IOException;
import java.util.*;

/**
 * @author RichieZhang
 * @create 2022-10-29 下午 4:43
 */
public class MapTest {

    @Test
    public void test1(){
        Map<String,Integer> map = new HashMap<>();
        map.put("AA",123);
        map.put("BB",111);
        map.put("CC",222);

        Set<String> keySet = map.keySet();
        for (String s : keySet) {
            System.out.println(s);
        }

        Collection<Integer> values = map.values();
        for (Integer value : values) {
            System.out.println(value);
        }

        Set<Map.Entry<String, Integer>> entrySet = map.entrySet();
        Iterator<Map.Entry<String, Integer>> iterator = entrySet.iterator();
        while (iterator.hasNext()){
            Map.Entry<String, Integer> entry = iterator.next();
            String key = entry.getKey();
            Integer value = entry.getValue();
            System.out.println(key + "===" + value);
        }
    }

    @Test
    public void test2(){
        List<String> list = new ArrayList<>();
        list.add("AA");
        list.add("BB");
        list.add("CC");

        Iterator<String> iterator = list.iterator();
        while (iterator.hasNext()){
            System.out.println(iterator.next());

        }
    }

    @Test
    public void test3(){
        HashMap<String,String> map = new HashMap<>();
        map.put("AA","123");
        map.put("BB","111");
        map.put("CC","222");
        System.out.println(getValueList(map));

    }

    public List<String> getValueList(HashMap<String,String> map){
        ArrayList<String> valueList = new ArrayList<>();
        Collection<String> values = map.values();
        for (String value : values){
            valueList.add(value);
        }

        return valueList;

    }

    @Test
    public void test4() throws IOException {
        File file = new File("hello.txt");

        File destFile = new File(file.getParent(),"he.txt");
        boolean newFile = destFile.createNewFile();
        if (newFile){
            System.out.println("创建成功！");
        }
    }
}