Java 不可编辑的Map

public class Test {

  public static void main(String[] args) {
    Map map = Collections.singletonMap("a", "abc");
    map.put("a", "bbb");
    System.out.println(map);
  }

}

Exception in thread "main" java.lang.UnsupportedOperationException
	at java.base/java.util.AbstractMap.put(AbstractMap.java:209)
	at org.example.test.Test.main(Test.java:18)