@throws nullpointerexception if the entry is null
@param pair the pair to copy, must not be null
file : https_github_com_apache_commons-collections_git/src/main/java/org/apache/commons/collections4/keyvalue/UnmodifiableMapEntry.java
file : https_github_com_apache_commons-collections_git/src/main/java/org/apache/commons/collections4/keyvalue/DefaultMapEntry.java
file : https_github_com_apache_commons-collections_git/src/main/java/org/apache/commons/collections4/keyvalue/DefaultKeyValue.java