Read this chart eight, you learn java is half the battle!

1. String invariance
following diagram shows what happens following code:
String = S "ABCD";
S = S. concat ( "EF");
2. the equals () and hashCode () contract
HashCode designed to improve performance. agreement between () the equals () and hasCode is:
1. If two objects are equal, they must have the same hash code.
2. If the two objects have the same hash code, they may be equal or may not be equal.
3. Java exception class hierarchy
red is a checked exception must be caught or declared in the throws clause of the method.
4. collection class hierarchy
Note the difference between the set and set.
5. Java synchronization
Java synchronization mechanism can be illustrated by analogy.
6. aliasing
alias aliases means may update a plurality of positions, and different types of these aliases.
Stack and heap 7.
This figure shows the location of the object in memory and a method at runtime.
8. The JVM runtime data area
which shows the entire JVM runtime data area.
Finally, the development of so many years I have summarized the data and interview questions a learning Java, if you want to upgrade their technology above, you can follow me, private letters sent to receive information or comments area to leave their contact details, time remember to help me make the point under forward with more people see Oh.