Where can I find the following classes in Java
<p>I am a .NET dev learning Java. As a result, I understand all the fundamentals of programming like loops, variables, functions, etc. My biggest bottleneck is that I don't know my way around Java's packages like I do with .NET's.</p>

<p>This is the reason for this thread - where do I find the following functionality in Java?:</p>

<p>System.Diagnostics - where can I use things like stopwatch, programmatic breakpoints and loggers?</p>

<p>Is there a Java equivalent of .NET performance counters?</p>

<p>What are weak keys in Java? I just came across a collection which uses weak keys in Java so am asking here. :)</p>

<p>Thanks</p>
