Notes 30

CS205 Notes 30 (1 November 2006)

Upcoming Schedule

Now — project idea description

Monday, November 6: Quiz 4

Friday, November 10 (beginning of class) — project design document

week of November 13 — project design reviews

week of November 27 — project progress reports

Monday, December 4 (in class) — project presentations/demos

Tuesday, December 5 (before 5pm) — project final reports including code and teammate assessments

Selected JavaVM Instructions

Opcode	Mnemonic	Description
0	`nop`	Does nothing
1	`aconst_null`	Push null on the stack
3	`iconst_0`	Push int 0 on the stack
4	`iconst_1`	Push int 1 on the stack
8	`iconst_5`	Push int 5 on the stack
9	`lconst_0`	Push long 0 on the stack
...	...	...
21	`iload varnum`	Push the int value in local variable varnum on the stack
22	`lload varnum`	Push the long value in local variable varnum on the stack
23	`fload varnum`	Push the float value in local variable varnum on the stack
24	`dload varnum`	Push the double value in local variable varnum on the stack
25	`aload varnum`	Push the object reference in local variable varnum on the stack
26	`iload_0`	Push the int value in local variable 0 on the stack
27	`iload_1`	Push the int value in local variable 1 on the stack
	...	...	...
45	`aload_3`	Push the object reference in local variable 3 on the stack
...	...	...
54	`istore varnum`	Store the int value at the top of the stack in local variable varnum and pop it from stack
58	`astore varnum`	Store the object reference at the top of the stack in local variable varnum and pop it from stack
...	...	...
45	`aload_3`	Push the object reference in local variable 3 on the stack
	...	...	...
87	`pop`	Pops the top (single word) off the stack
88	`pop2`	Pops the top two words off the stack
89	`dup`	Pops the top of the stack, and pushes that value twice
...	...	...
96	`iadd`	Pops two ints off the stack, and pushes their sum
97	`ladd`	Pops two longs off the stack, and pushes their sum
104	`imul`	Pops two ints off the stack, and pushes their product
116	`ineg`	Pops an int off the stack, and pushes its negation
153	`ifeq label`	Pops an int off the stack, if it is zero, jump to label
154	`ifne label`	Pops an int off the stack, if it is not zero, jump to label
165	`if_acmpeq label`	Pops two object references off the stack, if they are equal (same object), jump to label
167	`goto label`	Causes execution to jump to label
172	`ireturn`	Pops an int off the stack, and pushes it onto the caller's stack. Discards all other items on this method's stack. Causes execution to contion at the call site.
180	`getfield field`	Pops an object reference from the stack, and pushes the value of the specified field of that object on the stack
181	`putfield field`	Pops a value and an object reference from the stack, and store the value in the specified field of that object
182	`invokevirtual method`	Pops an object reference from the stack, and invokes the specified method on that object; pops the parameters from the stack, and stores them in local variables
183	`invokespecial method`	Pops an object reference from the stack, and invokes the specified method on that object; pops the parameters from the stack, and stores them in local variables. (Used for constructors, private methods and `super` invocations.)
184	`invokestatic method`	Invokes the specified static method; pops the parameters from the stack, and stores them in local variables
187	`new class`	Pushes an object reference to a new object of type class
188	`newarray type`	Pops an integer off the stack, and pushes a reference to a new array of the specified type and the size of the popped integer
...	...	...
201	`jsr_w label`	Jump to a subroutine using a wide offset (useful for exception handling)

For a complete description of all the JavaVM instructions, see The Java^TM Virtual Machine Specification.

To examine the byte codes the compiler produces for a class:

Start a DOS shell by selecting "Run" from the Start menu and entering "cmd"
cd to the directory containing the class file
java -p classname

Method void main(java.lang.String[])
   0 iconst_2
   1 istore_1
   2 iconst_3
   3 istore_2
   4 iload_1
   5 iload_2
   6 iadd
   7 istore_3
   8 getstatic #2 <Field java.io.PrintStream err>
  11 new #3 <Class java.lang.StringBuffer>
  14 dup
  15 invokespecial #4 <Method java.lang.StringBuffer()>
  18 ldc #5 <String "c: ">
  20 invokevirtual #6 <Method java.lang.StringBuffer
   append(java.lang.String)>
  23 iload_3
  24 invokevirtual #7 <Method java.lang.StringBuffer append(int)>
  27 invokevirtual #8 <Method java.lang.String toString()>
  30 invokevirtual #9 <Method void println(java.lang.String)>
  33 return