Iterating over and deleting from Hashtable in Java

Question

I have a Hashtable in Java and want to iterate over all the values in the table and delete a particular key-value pair while iterating    How may this be done

User · Answer

You can use a temporary deletion list   List lt String gt  keyList   new ArrayList lt String gt    for Map Entry lt String String gt  entry   hashTable     if entry getValue   equals  delete       replace with your own check     keyList add entry getKey        for String key   keyList     hashTable remove key       You can find more information about Hashtable methods in the Java API

User · Answer

You need to use an explicit java util Iterator to iterate over the Map s entry set rather than being able to use the enhanced For-loop syntax available in Java 6   The following example iterates over a Map of Integer  String pairs  removing any entry whose Integer key is null or equals 0   Map lt Integer  String gt  map        Iterator lt Map Entry lt Integer  String gt  gt  it   map entrySet   iterator     while  it hasNext        Map Entry lt Integer  String gt  entry   it next          Remove entry if key is null or equals 0    if  entry getKey      null    entry getKey      0        it remove

User · Answer

So you know the key  value pair that you want to delete in advance  It s just much clearer to do this  then    table delete key    for  K key  table keySet             do whatever you need to do with the rest of the keys

User · Answer

You can use Enumeration   Hashtable lt Integer  String gt  table        Enumeration lt Integer gt  enumKey   table keys    while enumKey hasMoreElements          Integer key   enumKey nextElement        String val   table get key       if key  0  amp  amp  val equals  0            table remove key

[java] Iterating over and deleting from Hashtable in Java

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