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)