How does Increment operator work in Java?

How does the instanceof operator work in Java?

• Under the covers, in as much detail as you know.

• Answer:

  The instanceof operator, like the rest of Java, works at both the compiler level and at the virtual machine level. At compile time, the instanceof is checked and compiled into byte code. The checks are detailed in the Java Language Specification: http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.20.2 The left side must be a reference or null, and not a primitive type. The right side must be a non-generic type, even if it is a generic class. For example, java.util.List<T> is not allowed. This shows that generic types are erased at runtime. The compile-time type of the left side must allow casting to the right side. instanceof should only be used for downcasting, in most cases. At runtime, the check is detailed in the Java Virtual Machine Specification: http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-6.html#jvms-6.5.instanceof To quote, with the statement being S instanceof T, the result is true if and only if: If S is an ordinary (nonarray) class, then: If T is a class type, then S must be the same class as T, or S must be a subclass of T; If T is an interface type, then S must implement interface T. If S is an interface type, then: If T is a class type, then T must be Object. If T is an interface type, then T must be the same interface as S or a superinterface of S. If S is a class representing the array type SC[], that is, an array of components of type SC, then: If T is a class type, then T must be Object. If T is an interface type, then T must be one of the interfaces implemented by arrays (JLS §4.10.3). If T is an array type TC[], that is, an array of components of type TC, then one of the following must be true: TC and SC are the same primitive type. TC and SC are reference types, and type SC can be cast to TC by these run-time rules