The following prompt was entered into Microsoft CoPilot, with no follow up prompts. Note the typo where the word computer should have been computes. This did not cause any problems for the LLM.
Write a Java Program to output the nth fibonacci number where the user inputs n.
Include a method called fibonacci(n) which computer the nth fibonacci number
iteratively.
The high level language typically gets compiled to machine language. In java, that machine language is ByteCode, which itself is interpreted by the Java Virtual Machine or compiled to the hardware's machine language at runtime with a Just-In-Time compiler (JIT). CoPilot generated two solutions to this prompt. This one uses long values for the result. The other version, not shown, used BigIntegers allowing it to handle inputs greater than 92.
import java.util.Scanner;
public class Fibonacci {
// Computes the nth Fibonacci number iteratively (0-based: F(0)=0, F(1)=1)
public static long fibonacci(int n) {
if (n < 0) {
throw new IllegalArgumentException("n must be non-negative.");
}
if (n == 0) return 0L;
if (n == 1) return 1L;
long prev = 0L; // F(0)
long curr = 1L; // F(1)
for (int i = 2; i <= n; i++) {
long next = prev + curr;
prev = curr;
curr = next;
}
return curr;
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter n (non-negative integer): ");
if (!scanner.hasNextInt()) {
System.out.println("Invalid input. Please enter a non-negative integer.");
return;
}
int n = scanner.nextInt();
if (n < 0) {
System.out.println("n must be non-negative.");
return;
}
if (n > 92) {
System.out.println("Warning: n > 92 will overflow a 64-bit long. Try the BigInteger version below.");
}
long result = fibonacci(n);
System.out.println("F(" + n + ") = " + result);
}
}
Assembly language is a human readable form or machine instructions. A Java class can be disassembled into a type of assembly using the javap command. Unlike traditional compiled languages, there is no assembler in the Java Development Kit.
Compiled from "Fibonacci.java"
public class Fibonacci {
public Fibonacci();
Code:
0: aload_0
1: invokespecial #8 // Method java/lang/Object."<init>":()V
4: return
LineNumberTable:
line 12: 0
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 this LFibonacci;
public static long fibonacci(int);
Code:
0: iload_0
1: ifge 14
4: new #16 // class java/lang/IllegalArgumentException
7: dup
8: ldc #18 // String n must be non-negative.
10: invokespecial #20 // Method java/lang/IllegalArgumentException."<init>":(Ljava/lang/String;)V
13: athrow
14: iload_0
15: ifne 20
18: lconst_0
19: lreturn
20: iload_0
21: iconst_1
22: if_icmpne 27
25: lconst_1
26: lreturn
27: lconst_0
28: lstore_1
29: lconst_1
30: lstore_3
31: iconst_2
32: istore 5
34: goto 50
37: lload_1
38: lload_3
39: ladd
40: lstore 6
42: lload_3
43: lstore_1
44: lload 6
46: lstore_3
47: iinc 5, 1
50: iload 5
52: iload_0
53: if_icmple 37
56: lload_3
57: lreturn
LineNumberTable:
line 16: 0
line 17: 4
line 19: 14
line 20: 20
line 22: 27
line 23: 29
line 25: 31
line 26: 37
line 27: 42
line 28: 44
line 25: 47
line 30: 56
LocalVariableTable:
Start Length Slot Name Signature
0 58 0 n I
29 29 1 prev J
31 27 3 curr J
34 22 5 i I
42 5 6 next J
public static void main(java.lang.String[]);
Code:
0: new #33 // class java/util/Scanner
3: dup
4: getstatic #35 // Field java/lang/System.in:Ljava/io/InputStream;
7: invokespecial #41 // Method java/util/Scanner."<init>":(Ljava/io/InputStream;)V
10: astore_1
11: getstatic #44 // Field java/lang/System.out:Ljava/io/PrintStream;
14: ldc #48 // String Enter n (non-negative integer):
16: invokevirtual #50 // Method java/io/PrintStream.print:(Ljava/lang/String;)V
19: aload_1
20: invokevirtual #55 // Method java/util/Scanner.hasNextInt:()Z
23: ifne 35
26: getstatic #44 // Field java/lang/System.out:Ljava/io/PrintStream;
29: ldc #59 // String Invalid input. Please enter a non-negative integer.
31: invokevirtual #61 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
34: return
35: aload_1
36: invokevirtual #64 // Method java/util/Scanner.nextInt:()I
39: istore_2
40: iload_2
41: ifge 53
44: getstatic #44 // Field java/lang/System.out:Ljava/io/PrintStream;
47: ldc #18 // String n must be non-negative.
49: invokevirtual #61 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
52: return
53: iload_2
54: bipush 92
56: if_icmple 67
59: getstatic #44 // Field java/lang/System.out:Ljava/io/PrintStream;
62: ldc #68 // String Warning: n > 92 will overflow a 64-bit long. Try the BigInteger version below.
64: invokevirtual #61 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
67: iload_2
68: invokestatic #70 // Method fibonacci:(I)J
71: lstore_3
72: getstatic #44 // Field java/lang/System.out:Ljava/io/PrintStream;
75: iload_2
76: lload_3
77: invokedynamic #72, 0 // InvokeDynamic #0:makeConcatWithConstants:(IJ)Ljava/lang/String;
82: invokevirtual #61 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
85: return
LineNumberTable:
line 34: 0
line 35: 11
line 36: 19
line 37: 26
line 38: 34
line 41: 35
line 42: 40
line 43: 44
line 44: 52
line 46: 53
line 47: 59
line 50: 67
line 51: 72
line 52: 85
LocalVariableTable:
Start Length Slot Name Signature
0 86 0 args [Ljava/lang/String;
11 75 1 scanner Ljava/util/Scanner;
40 46 2 n I
72 14 3 result J
}
Java ByteCode is the machine language of the Java Virtual Machine. It is stored in a binary file. The listing below shows the hexadecimal form of the binary in a typeical format for binary file dumps (created using the program hexdump). The dump shows three columns. The first column is the index of the line in hex. For example, the fourth line consists of 16 bytes starting at address 0x00000030 (48 in decimal). The second column is the actual binary data encoded as hex (digits 0..9,a..f). All Java class files start with the 4 byte value 0xcafebabe. The last column shows the character representation of any bytes which are in the range of ASCII printable characters. Other values are displayed as a period.
|Address | Data - two hex digits/byte (16 bytes/line) |Printable Chars |
|00000000| ca fe ba be 00 00 00 44 00 62 07 00 02 01 00 09 |.......D.b......|
|00000010| 46 69 62 6f 6e 61 63 63 69 07 00 04 01 00 10 6a |Fibonacci......j|
|00000020| 61 76 61 2f 6c 61 6e 67 2f 4f 62 6a 65 63 74 01 |ava/lang/Object.|
|00000030| 00 06 3c 69 6e 69 74 3e 01 00 03 28 29 56 01 00 |..<init>...()V..|
|00000040| 04 43 6f 64 65 0a 00 03 00 09 0c 00 05 00 06 01 |.Code...........|
|00000050| 00 0f 4c 69 6e 65 4e 75 6d 62 65 72 54 61 62 6c |..LineNumberTabl|
|00000060| 65 01 00 12 4c 6f 63 61 6c 56 61 72 69 61 62 6c |e...LocalVariabl|
|00000070| 65 54 61 62 6c 65 01 00 04 74 68 69 73 01 00 0b |eTable...this...|
|00000080| 4c 46 69 62 6f 6e 61 63 63 69 3b 01 00 09 66 69 |LFibonacci;...fi|
|00000090| 62 6f 6e 61 63 63 69 01 00 04 28 49 29 4a 07 00 |bonacci...(I)J..|
|000000a0| 11 01 00 22 6a 61 76 61 2f 6c 61 6e 67 2f 49 6c |..."java/lang/Il|
|000000b0| 6c 65 67 61 6c 41 72 67 75 6d 65 6e 74 45 78 63 |legalArgumentExc|
|000000c0| 65 70 74 69 6f 6e 08 00 13 01 00 17 6e 20 6d 75 |eption......n mu|
|000000d0| 73 74 20 62 65 20 6e 6f 6e 2d 6e 65 67 61 74 69 |st be non-negati|
|000000e0| 76 65 2e 0a 00 10 00 15 0c 00 05 00 16 01 00 15 |ve..............|
|000000f0| 28 4c 6a 61 76 61 2f 6c 61 6e 67 2f 53 74 72 69 |(Ljava/lang/Stri|
|00000100| 6e 67 3b 29 56 01 00 01 6e 01 00 01 49 01 00 04 |ng;)V...n...I...|
|00000110| 70 72 65 76 01 00 01 4a 01 00 04 63 75 72 72 01 |prev...J...curr.|
|00000120| 00 01 69 01 00 04 6e 65 78 74 01 00 0d 53 74 61 |..i...next...Sta|
|00000130| 63 6b 4d 61 70 54 61 62 6c 65 01 00 04 6d 61 69 |ckMapTable...mai|
|00000140| 6e 01 00 16 28 5b 4c 6a 61 76 61 2f 6c 61 6e 67 |n...([Ljava/lang|
|00000150| 2f 53 74 72 69 6e 67 3b 29 56 07 00 22 01 00 11 |/String;)V.."...|
|00000160| 6a 61 76 61 2f 75 74 69 6c 2f 53 63 61 6e 6e 65 |java/util/Scanne|
|00000170| 72 09 00 24 00 26 07 00 25 01 00 10 6a 61 76 61 |r..$.&..%...java|
|00000180| 2f 6c 61 6e 67 2f 53 79 73 74 65 6d 0c 00 27 00 |/lang/System..'.|
|00000190| 28 01 00 02 69 6e 01 00 15 4c 6a 61 76 61 2f 69 |(...in...Ljava/i|
|000001a0| 6f 2f 49 6e 70 75 74 53 74 72 65 61 6d 3b 0a 00 |o/InputStream;..|
|000001b0| 21 00 2a 0c 00 05 00 2b 01 00 18 28 4c 6a 61 76 |!.*....+...(Ljav|
|000001c0| 61 2f 69 6f 2f 49 6e 70 75 74 53 74 72 65 61 6d |a/io/InputStream|
|000001d0| 3b 29 56 09 00 24 00 2d 0c 00 2e 00 2f 01 00 03 |;)V..$.-..../...|
|000001e0| 6f 75 74 01 00 15 4c 6a 61 76 61 2f 69 6f 2f 50 |out...Ljava/io/P|
|000001f0| 72 69 6e 74 53 74 72 65 61 6d 3b 08 00 31 01 00 |rintStream;..1..|
|00000200| 20 45 6e 74 65 72 20 6e 20 28 6e 6f 6e 2d 6e 65 | Enter n (non-ne|
|00000210| 67 61 74 69 76 65 20 69 6e 74 65 67 65 72 29 3a |gative integer):|
|00000220| 20 0a 00 33 00 35 07 00 34 01 00 13 6a 61 76 61 | ..3.5..4...java|
|00000230| 2f 69 6f 2f 50 72 69 6e 74 53 74 72 65 61 6d 0c |/io/PrintStream.|
|00000240| 00 36 00 16 01 00 05 70 72 69 6e 74 0a 00 21 00 |.6.....print..!.|
|00000250| 38 0c 00 39 00 3a 01 00 0a 68 61 73 4e 65 78 74 |8..9.:...hasNext|
|00000260| 49 6e 74 01 00 03 28 29 5a 08 00 3c 01 00 33 49 |Int...()Z..<..3I|
|00000270| 6e 76 61 6c 69 64 20 69 6e 70 75 74 2e 20 50 6c |nvalid input. Pl|
|00000280| 65 61 73 65 20 65 6e 74 65 72 20 61 20 6e 6f 6e |ease enter a non|
|00000290| 2d 6e 65 67 61 74 69 76 65 20 69 6e 74 65 67 65 |-negative intege|
|000002a0| 72 2e 0a 00 33 00 3e 0c 00 3f 00 16 01 00 07 70 |r...3.>..?.....p|
|000002b0| 72 69 6e 74 6c 6e 0a 00 21 00 41 0c 00 42 00 43 |rintln..!.A..B.C|
|000002c0| 01 00 07 6e 65 78 74 49 6e 74 01 00 03 28 29 49 |...nextInt...()I|
|000002d0| 08 00 45 01 00 4e 57 61 72 6e 69 6e 67 3a 20 6e |..E..NWarning: n|
|000002e0| 20 3e 20 39 32 20 77 69 6c 6c 20 6f 76 65 72 66 | > 92 will overf|
|000002f0| 6c 6f 77 20 61 20 36 34 2d 62 69 74 20 6c 6f 6e |low a 64-bit lon|
|00000300| 67 2e 20 54 72 79 20 74 68 65 20 42 69 67 49 6e |g. Try the BigIn|
|00000310| 74 65 67 65 72 20 76 65 72 73 69 6f 6e 20 62 65 |teger version be|
|00000320| 6c 6f 77 2e 0a 00 01 00 47 0c 00 0e 00 0f 12 00 |low.....G.......|
|00000330| 00 00 49 0c 00 4a 00 4b 01 00 17 6d 61 6b 65 43 |..I..J.K...makeC|
|00000340| 6f 6e 63 61 74 57 69 74 68 43 6f 6e 73 74 61 6e |oncatWithConstan|
|00000350| 74 73 01 00 16 28 49 4a 29 4c 6a 61 76 61 2f 6c |ts...(IJ)Ljava/l|
|00000360| 61 6e 67 2f 53 74 72 69 6e 67 3b 01 00 04 61 72 |ang/String;...ar|
|00000370| 67 73 01 00 13 5b 4c 6a 61 76 61 2f 6c 61 6e 67 |gs...[Ljava/lang|
|00000380| 2f 53 74 72 69 6e 67 3b 01 00 07 73 63 61 6e 6e |/String;...scann|
|00000390| 65 72 01 00 13 4c 6a 61 76 61 2f 75 74 69 6c 2f |er...Ljava/util/|
|000003a0| 53 63 61 6e 6e 65 72 3b 01 00 06 72 65 73 75 6c |Scanner;...resul|
|000003b0| 74 01 00 0a 53 6f 75 72 63 65 46 69 6c 65 01 00 |t...SourceFile..|
|000003c0| 0e 46 69 62 6f 6e 61 63 63 69 2e 6a 61 76 61 01 |.Fibonacci.java.|
|000003d0| 00 10 42 6f 6f 74 73 74 72 61 70 4d 65 74 68 6f |..BootstrapMetho|
|000003e0| 64 73 0a 00 55 00 57 07 00 56 01 00 24 6a 61 76 |ds..U.W..V..$jav|
|000003f0| 61 2f 6c 61 6e 67 2f 69 6e 76 6f 6b 65 2f 53 74 |a/lang/invoke/St|
|00000400| 72 69 6e 67 43 6f 6e 63 61 74 46 61 63 74 6f 72 |ringConcatFactor|
|00000410| 79 0c 00 4a 00 58 01 00 98 28 4c 6a 61 76 61 2f |y..J.X...(Ljava/|
|00000420| 6c 61 6e 67 2f 69 6e 76 6f 6b 65 2f 4d 65 74 68 |lang/invoke/Meth|
|00000430| 6f 64 48 61 6e 64 6c 65 73 24 4c 6f 6f 6b 75 70 |odHandles$Lookup|
|00000440| 3b 4c 6a 61 76 61 2f 6c 61 6e 67 2f 53 74 72 69 |;Ljava/lang/Stri|
|00000450| 6e 67 3b 4c 6a 61 76 61 2f 6c 61 6e 67 2f 69 6e |ng;Ljava/lang/in|
|00000460| 76 6f 6b 65 2f 4d 65 74 68 6f 64 54 79 70 65 3b |voke/MethodType;|
|00000470| 4c 6a 61 76 61 2f 6c 61 6e 67 2f 53 74 72 69 6e |Ljava/lang/Strin|
|00000480| 67 3b 5b 4c 6a 61 76 61 2f 6c 61 6e 67 2f 4f 62 |g;[Ljava/lang/Ob|
|00000490| 6a 65 63 74 3b 29 4c 6a 61 76 61 2f 6c 61 6e 67 |ject;)Ljava/lang|
|000004a0| 2f 69 6e 76 6f 6b 65 2f 43 61 6c 6c 53 69 74 65 |/invoke/CallSite|
|000004b0| 3b 0f 06 00 54 08 00 5b 01 00 08 46 28 01 29 20 |;...T..[...F(.) |
|000004c0| 3d 20 01 01 00 0c 49 6e 6e 65 72 43 6c 61 73 73 |= ....InnerClass|
|000004d0| 65 73 07 00 5e 01 00 25 6a 61 76 61 2f 6c 61 6e |es..^..%java/lan|
|000004e0| 67 2f 69 6e 76 6f 6b 65 2f 4d 65 74 68 6f 64 48 |g/invoke/MethodH|
|000004f0| 61 6e 64 6c 65 73 24 4c 6f 6f 6b 75 70 07 00 60 |andles$Lookup..`|
|00000500| 01 00 1e 6a 61 76 61 2f 6c 61 6e 67 2f 69 6e 76 |...java/lang/inv|
|00000510| 6f 6b 65 2f 4d 65 74 68 6f 64 48 61 6e 64 6c 65 |oke/MethodHandle|
|00000520| 73 01 00 06 4c 6f 6f 6b 75 70 00 21 00 01 00 03 |s...Lookup.!....|
|00000530| 00 00 00 00 00 03 00 01 00 05 00 06 00 01 00 07 |................|
|00000540| 00 00 00 2f 00 01 00 01 00 00 00 05 2a b7 00 08 |.../........*...|
|00000550| b1 00 00 00 02 00 0a 00 00 00 06 00 01 00 00 00 |................|
|00000560| 0c 00 0b 00 00 00 0c 00 01 00 00 00 05 00 0c 00 |................|
|00000570| 0d 00 00 00 09 00 0e 00 0f 00 01 00 07 00 00 00 |................|
|00000580| ca 00 04 00 08 00 00 00 3a 1a 9c 00 0d bb 00 10 |........:.......|
|00000590| 59 12 12 b7 00 14 bf 1a 9a 00 05 09 ad 1a 04 a0 |Y...............|
|000005a0| 00 05 0a ad 09 40 0a 42 05 36 05 a7 00 10 1f 21 |.....@.B.6.....!|
|000005b0| 61 37 06 21 40 16 06 42 84 05 01 15 05 1a a4 ff |a7.!@..B........|
|000005c0| f0 21 ad 00 00 00 03 00 0a 00 00 00 32 00 0c 00 |.!..........2...|
|000005d0| 00 00 10 00 04 00 11 00 0e 00 13 00 14 00 14 00 |................|
|000005e0| 1b 00 16 00 1d 00 17 00 1f 00 19 00 25 00 1a 00 |............%...|
|000005f0| 2a 00 1b 00 2c 00 1c 00 2f 00 19 00 38 00 1e 00 |*...,.../...8...|
|00000600| 0b 00 00 00 34 00 05 00 00 00 3a 00 17 00 18 00 |....4.....:.....|
|00000610| 00 00 1d 00 1d 00 19 00 1a 00 01 00 1f 00 1b 00 |................|
|00000620| 1b 00 1a 00 03 00 22 00 16 00 1c 00 18 00 05 00 |......".........|
|00000630| 2a 00 05 00 1d 00 1a 00 06 00 1e 00 00 00 0c 00 |*...............|
|00000640| 05 0e 05 06 fe 00 09 04 04 01 0c 00 09 00 1f 00 |................|
|00000650| 20 00 01 00 07 00 00 00 e5 00 04 00 05 00 00 00 | ...............|
|00000660| 56 bb 00 21 59 b2 00 23 b7 00 29 4c b2 00 2c 12 |V..!Y..#..)L..,.|
|00000670| 30 b6 00 32 2b b6 00 37 9a 00 0c b2 00 2c 12 3b |0..2+..7.....,.;|
|00000680| b6 00 3d b1 2b b6 00 40 3d 1c 9c 00 0c b2 00 2c |..=.+..@=......,|
|00000690| 12 12 b6 00 3d b1 1c 10 5c a4 00 0b b2 00 2c 12 |....=...\.....,.|
|000006a0| 44 b6 00 3d 1c b8 00 46 42 b2 00 2c 1c 21 ba 00 |D..=...FB..,.!..|
|000006b0| 48 00 00 b6 00 3d b1 00 00 00 03 00 0a 00 00 00 |H....=..........|
|000006c0| 3a 00 0e 00 00 00 22 00 0b 00 23 00 13 00 24 00 |:....."...#...$.|
|000006d0| 1a 00 25 00 22 00 26 00 23 00 29 00 28 00 2a 00 |..%.".&.#.).(.*.|
|000006e0| 2c 00 2b 00 34 00 2c 00 35 00 2e 00 3b 00 2f 00 |,.+.4.,.5...;./.|
|000006f0| 43 00 32 00 48 00 33 00 55 00 34 00 0b 00 00 00 |C.2.H.3.U.4.....|
|00000700| 2a 00 04 00 00 00 56 00 4c 00 4d 00 00 00 0b 00 |*.....V.L.M.....|
|00000710| 4b 00 4e 00 4f 00 01 00 28 00 2e 00 17 00 18 00 |K.N.O...(.......|
|00000720| 02 00 48 00 0e 00 50 00 1a 00 03 00 1e 00 00 00 |..H...P.........|
|00000730| 0d 00 03 fc 00 23 07 00 21 fc 00 11 01 0d 00 03 |.....#..!.......|
|00000740| 00 51 00 00 00 02 00 52 00 53 00 00 00 08 00 01 |.Q.....R.S......|
|00000750| 00 59 00 01 00 5a 00 5c 00 00 00 0a 00 01 00 5d |.Y...Z.\.......]|
|00000760| 00 5f 00 61 00 19 |._.a..|
|00000766|