.class public Factorial
.super java/lang/Object 

.method public <init>()V 
    aload 0
    invokenonvirtual java/lang/Object/<init>()V
    return
.end method

.method public static factorial(I)I ; calc `given`!
    .limit locals 3
    .limit stack  2
    ; note that parameters are automatically stored as
    ; local variables, we dont need to do `istore 0` to
    ; store the given integer in a local variable.
    bipush 1 ; we start calculating with `p`=1
    istore 1 ; store `p`
    bipush 2 ; we start calculating with `j`=1
    istore 2 ; store `j`
    loop:
        ; p *= j
        iload 1         ; load p
        iload 2         ; load j
        imul            ; multiply p and j
        istore 1        ; store p*j in p

        ; j++
        iload 2         ; load j
        bipush 1        ; put a 1 on the stack
        iadd            ; add j and 1
        istore 2        ; store j+1 in j

        ; if j<given
        iload 2         ; load j
        iload 0         ; load given
        if_icmplt loop  ; if j < given goto loop

    ; else return given * p
    iload 0         ; load given
    iload 1         ; load p
    imul            ; multiply given and p

    ireturn          ; return given*p
.end method

.method public static main([Ljava/lang/String;)V
    .limit locals   3
    .limit stack    4
    ; parse cli args to int
    aload 0
    aaload 0
    invokestatic    java/lang/Integer/parseInt(Ljava/lang/String;)I
    istore 1

    ; format
    iload 1
    ldc "! = "
    iload 1
    invokestatic    Factorial/factorial(I)I ; call factorial
    invokevirtual   java/lang/String/format(ILjava/lang/String;I)I
    astore 2

    ; output
    getstatic       java/lang/System/out Ljava/io/PrintStream;
    aload 2         ; load formatted str
    invokevirtual   java/io/PrintStream/println(Ljava/lang/String;)V 
    return
.end method