浅谈Map集合中get不存在的key值,会抛出异常吗?

public static void main(String[] args)
{
 Map<String, String> a = new HashMap<String, String>();
 String string = a.get("a111");
 System.out.println(string);
}

public static void main(String[] args)
{
 Map<String, String> a = new HashMap<String, String>();
 String string = a.get("a111");
 System.out.println(string);
}

import java.util.HashMap;
import java.util.Map;
 
public class TestMapKey {
 public static void main(String[] args) {
 Map<Integer, String> map = new HashMap<Integer, String>();
 map.put(220180, null);
 map.put(220181, "马先生");
 System.out.println("get()方法的返回结果：");
 System.out.print("------ " + map.get(220180));
 System.out.print("  " + map.get(220181));
 System.out.println("  " + map.get(220182));
 System.out.println("containsKey()方法的返回结果：");
 System.out.print("------ " + map.containsKey(220180));
 System.out.print("  " + map.containsKey(220181));
 System.out.println("  " + map.containsKey(220182));
 }
}