|
|
Optimize with a SATA RAID Storage Solution
Range of capacities as low as $1250 per TB. Ideal if you currently rely on servers/disks/JBODs
Page 2 of 4
javac generates the following bytecode sequence for the remainder method:
The main bytecode sequence for remainder:
0 iload_0 // Push local variable 0 (arg passed as divisor)
1 iload_1 // Push local variable 1 (arg passed as dividend)
2 irem // Pop divisor, pop dividend, push remainder
3 ireturn // Return int on top of stack (the remainder)
The bytecode sequence for the catch (ArithmeticException) clause:
4 pop // Pop the reference to the ArithmeticException
// because it isn't used by this catch clause.
5 new #5 <Class DivideByZeroException>
// Create and push reference to new object of class
// DivideByZeroException.
DivideByZeroException
8 dup // Duplicate the reference to the new
// object on the top of the stack because it
// must be both initialized
// and thrown. The initialization will consume
// the copy of the reference created by the dup.
9 invokenonvirtual #9 <Method DivideByZeroException.<init>()V>
// Call the constructor for the DivideByZeroException
// to initialize it. This instruction
// will pop the top reference to the object.
12 athrow // Pop the reference to a Throwable object, in this
// case the DivideByZeroException,
// and throw the exception.
The bytecode sequence of the remainder method has two separate parts. The first part is the normal path of execution for the method. This part goes from pc offset
zero through three. The second part is the catch clause, which goes from pc offset four through twelve.
The irem instruction in the main bytecode sequence may throw an ArithmeticException. If this occurs, the Java virtual machine knows to jump to the bytecode sequence that implements the catch clause by looking
up and finding the exception in a table. Each method that catches exceptions is associated with an exception table that is
delivered in the class file along with the bytecode sequence of the method. The exception table has one entry for each exception
that is caught by each try block. Each entry has four pieces of information: the start and end points, the pc offset within
the bytecode sequence to jump to, and a constant pool index of the exception class that is being caught. The exception table
for the remainder method of class NitPickyMath is shown below:
Exception table:
from to target type
0 4 4 <Class java.lang.ArithmeticException>
The above exception table indicates that from pc offset zero through three, inclusive, ArithmeticException is caught. The try block's endpoint value, listed in the table under the label "to", is always one more than the last pc
offset for which the exception is caught. In this case the endpoint value is listed as four, but the last pc offset for which
the exception is caught is three. This range, zero to three inclusive, corresponds to the bytecode sequence that implements
the code inside the try block of remainder. The target listed in the table is the pc offset to jump to if an ArithmeticException is thrown between the pc offsets zero and three, inclusive.
If an exception is thrown during the execution of a method, the Java virtual machine searches through the exception table for a matching entry. An exception table entry matches if the current program counter is within the range specified by the entry, and if the exception class thrown is the exception class specified by the entry (or is a subclass of the specified exception class). The Java virtual machine searches through the exception table in the order in which the entries appear in the table. When the first match is found, the Java Virtual Machine sets the program counter to the new pc offset location and continues execution there. If no match is found, the Java virtual machine pops the current stack frame and rethrows the same exception. When the Java virtual machine pops the current stack frame, it effectively aborts execution of the current method and returns to the method that called this method. But instead of continuing execution normally in the previous method, it throws the same exception in that method, which causes the Java virtual machine to go through the same process of searching through the exception table of that method.