In Java Persistence API you use them to map a Java class with database tables. For example @Table () Used to map the particular Java class to the date base table. @Entity Represents that the class is an entity class. Similarly you can use many annotations to map individual columns, generate ids, generate version, relationships etc.
Since java.lang.String class override equals method, It return true if two String object contains same content but == will only return true if two references are pointing to same object. Here is an example of comparing two Strings in Java for equality using == and equals() method which will clear some doubts:
The flag Xmx specifies the maximum memory allocation pool for a Java Virtual Machine (JVM), while Xms specifies the initial memory allocation pool. This means that your JVM will be started with Xms amount of memory and will be able to use a maximum of Xmx amount of memory. For example, starting a JVM like below will start it with 256 MB of memory and will allow the process to use up to 2048 MB ...
It is the Bitwise xor operator in java which results 1 for different value of bit (ie 1 ^ 0 = 1) and 0 for same value of bit (ie 0 ^ 0 = 0) when a number is written in binary form.
In particular, if Java ever gets another ternary operator, people who use the term "conditional operator" will still be correct and unambiguous - unlike those who just say "ternary operator".
What is the Java ?: operator called and what does it do?