One Two Three questions

• Binary tree node keeping reference to its parent
• sort an array with minimum moves
• Java's buit-in libraries (or 3rd party code) to do base-conversions
• How does the order of elements in a HashSet work?
• type-cast rule in java
• Interpret a negative number as unsigned with BigInteger
• StringBuilder output does not include character supplied in the constructor
• how can more than one thread have "locked" on the same object (as shown in a thread-dump)
• If a class is loaded multiple times, do its static-members get initialized multiple times?
• why doesn't Java have "deep" wildcard import? [duplicate]

One Two Three answers