First tell me what is the best way to concatenate large number of String objects? Is it a + b? Most Java developers know not to use a + b (+ operator) because of huge performance problems, they use StringBuffer instead. In fact I did some tests in the past which confirms this folklore. However some of you may not know there is new kid on the block - StringBuilder.

This isn't a trick question. For a long time you couldn't delete a property from java.util.Properties class. In the recent versions too Java doesn't reveal that it has added the functionality. However as java.util.Properties now extends Hashtable, you can delete a property by: