I'm trying to make this program run, but I have one last error that I can't fix. I get an error message when trying to get user input in my lasTal() function. I am surprised about this error because the exact same line of code has worked for me in my other program.
import java.util.Scanner;
public class Nastaord{
public static int bFinal, cFinal;
public static int[] tallistaFinal;
private static int[] lasTal(){
int[] tallista; //Det vi ska ha talföljden i
int i = 0; //räknare för tallista
while(true){
System.out.print("Ange tal, eller tryck enter om du är klar: ");
String input = scanner.nextLine();
int nytt_tal = Integer.parseInt(input);
if(input == ""){
return tallista;}
tallista[i] = nytt_tal;
i++;
}
}
private static boolean bcFinns(int[] tallista){
boolean OK = true;
for(int b = -9; b <= 9; b++){
for(int c = -9; c <= 9; c++){
for(int i = tallista.length; i > 0;i--){
OK = tallista[i] == tallista[i-1]*b+c;
if(OK == false){
break;}
}
if(OK == true){
bFinal = b;
cFinal = c;
tallistaFinal = tallista;
return true;}
}
}
return false;
}
public static void main(String[] args){
boolean OK = bcFinns(lasTal());
if (OK == true){
System.out.print(tallistaFinal[tallistaFinal.length-1]*bFinal+cFinal);
}
if (OK == false){
System.out.print("No");
}
}
}
This is my error message:
Nastaord.java:13: error: cannot find symbol
String input = scanner.nextLine();
^
symbol: variable scanner
location: class Nastaord
Thanks
you did not creat a Scanner Object. Use this in lasTal() method at starting to take input from keyboard and u need to initialize "tallista " array.
Scanner scanner = new Scanner(System.in);
Related
So, I know that there are many people with this problem and many questions about it, but I just couldn't fin a solution for this, every other thing I try to execute works, but this doesn't and I can't figure out why...
package prob3;
public class LargestPrimeFactor {
double num = 600851475143D;
double LargestPrimeFactor;
public void getLargestPrimeFactor(String [] args){
double prevPrimeFactor = 0;
do {
for(double i = 0; i < num/2; i++){
if((num % i == 0) && (num / i != 1)){
prevPrimeFactor = num;
LargestPrimeFactor = num / i;
} else {
continue;
}
}
} while(prevPrimeFactor != LargestPrimeFactor);
System.out.println("The biggest prime factor of " + num + " is " + LargestPrimeFactor);
}
}
you should define a main function to run your program. Something like:
public static void main(String[] args) {
getLargestPrimeFactor(args);
}
I'm learning java and I'm having an issue with my if code not running.
In the following code I'm trying to determine if a number (variable num) is a triangle number (1,3, 6, 10 etc). The code should run through and give the "Is Triangle". However it keeps spitting out Null.
I understand this is not the most effective way to do this code, but I am trying to learn how to use Classes.
public class HelloWorld {
public static void main(String[] args) {
class NumberShape {
int num = 45;
int tri = 0;
int triplus = 0;
String triresult;
public String triangle() {
while (tri < num) {
if (tri == num) {
triresult = "Is a Triangle";
System.out.println("Is a Triangle");
} else if (tri + (triplus + 1) > num){
triresult = "Is Not a Triangle";
} else {
triplus++;
tri = tri + triplus;
}
}
return triresult;
}
}
NumberShape result = new NumberShape();
System.out.println(result.triangle());
}
}
Thanks for any help provided.
Try this code :
public class HelloWorld {
public static void main(String[] args) {
class NumberShape {
int num = 10;//Try other numbers
int tri = 0;
int triplus = 0;
int res = 0;
String triresult = "Is Not a Triangle";
int[] tab= new int[num];
public String triangle() {
//to calculate the triangle numbers
for(int i = 0; i<num; i++){
res = res + i;
tab[i]=res;
}
//To check if num is a triangle or not
for(int i = 0; i<tab.length; i++){
System.out.println(">> " + i + " : " + tab[i]);
if(tab[i]== num){
triresult = num + " Is a Triangle";
break;//Quit if the condition is checked
}else{
triresult = num + " Is Not a Triangle";
}
}
return triresult;
}
}
NumberShape result = new NumberShape();
System.out.println(result.triangle());
}
}
Hope this Helps.
Step through the loop carefully. You'll probably see that there is a case where
(tri < num)
fails, and thus you fall out of the loop, while
(tri == num)
and
(tri + (triplus + 1) > num)
both fail too, so no text gets set before you fall out.
You probably want to do your if-tests within the method on just tri, not a modification of tri, so as to reduce your own confusion about how the code is working.
I'm making a really simple app in java code, but for some reason it doesnt work. its a palindrome checker.
here is the code.
MAIN:
public class main {
public static void main(String[] args) {
Palindroom.palindroomChecker("RACECAR");
}
}
`Palindroom class:
public class Palindroom {
public static void palindroomChecker(String input) {
String omgekeerd = "";
boolean isPalindroom = false;
int length = input.length();
for(int i = 0; i < length; i++ ) {
String hulp = "" + input.charAt(i);
omgekeerd = omgekeerd + hulp;
}
System.out.println(omgekeerd);
System.out.println(input);
if(omgekeerd.equals(input)){
System.out.println("DIT IS EEN PALINDROOM!");
}
else {
System.out.println("HELAAS, DIT IS GEEN PALINDROOM!");
}
}
}`
For some reason the check in the if-statement doesnt go as it has to go. As you can see i checked omgekeerd and input and i also checked earlier the length of omgekeerd to see if there were clear spaces.
Can someone help me out!
thanks in advance
greetings Mauro Palsgraaf
Your logic is flawed. You're reconstructing a new string by appending every char of the input, in the same order, and then check that both strings are equal. So your method always says that the input is a palindrome.
You should construct a new string by appending the chars in the reverse order.
Or you could make it faster by checking that the nth character is the same as the character at the length - 1 - n position, for each n between 0 and length / 2.
You are not actually reversing the string, looks like omgekeerd will be in the same order as input.
Replace for with for(int i = length-1; i >= 0; i--) {
This can be simplified a lot
boolean isPalindrome = new StringBuilder(input).reverse().equals(input);
Maybe this would work for you?
String str = "madam i'm adam."; // String to compare
str = str.replaceAll("[//\\s,',,,.]",""); // Remove special characters
int len = str.length();
boolean isSame = false;
for(int i =0; i<len;i++){
if(str.charAt(i) == str.charAt(len-1-i)){
isSame = true;
}
else{
isSame = false;
break;
}
}
if(isSame){
System.out.print("Equal");
}
else{
System.out.print("Not equal");
}
i=0;
j=str.length()-1; //length of given string
String str; // your input string
while((i<j)||(i!=j)){
if(str.charAt(i)!=str.charAt(j)){
System.out.println("not palindrome");
break;
}
i++;
j--;
}
System.out.print("palindrome");
//this can used for checking without the need of generating and storing a reverse string
I am coding a Fibonacci sequence in Eclipse and this is my code-
public class FibonacciAlgorithm {
private int a = 0;
private int b = 1;
public FibonacciAlgorithm() {
}
public int increment() {
int temp = b;
b = a + b;
a = temp;
return value;
}
public int getValue() {
return b;
}
}
It is showing an error in the return value; line saying value cannot be resolved to a variable. I don't see any other errors.
Where is value defined? You return something that was not defined anywhere.
You don't have a "value" defined, this is your error. I don't remember the thing exactly, but I think you don't need a and b, I found this in my code archive, hope it helps.
public class Fibonacci
{
public static long fibo(int n)
{
if (n <= 1) return n;
else return fibo(n - 1) + fibo(n - 2);
}
public static void main() {
int count = 5; // change accordingly, bind to input etc.
int N = Integer.parseInt(count);
for (int i = 1; i <= N; i++)
System.out.println(i + ": " + fibo(i));
}
}
In case you want to stay with your own code, try returning "b" as value.
Your method is returning an int variable so you would have to define and return value as an int
I am not sure what you trying to do.
If you have "getValue" method I think "increment" method should be void.
When you want current Fibonacci value use "getValue" method.
public class FibonacciAlgorithm {
private int a = 0;
private int b = 1;
public FibonacciAlgorithm() {
}
public void increment() {
int temp = b;
b = a + b;
a = temp;
}
public int getValue() {
return b;
}
I need to encode and decode BER data. .NET has the class System.DirectoryServices.Protocols.BerConverter
The static method requires me to enter a string in the first parameter as shown below
byte[] oid = { 0x30, 0xD, 0x6, 0x9, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0xD, 0x1, 0x1, 0x1, 0x5, 0x0 }; // Object ID for RSA
var result2 = System.DirectoryServices.Protocols.BerConverter.Decoding("?what goes here?", oid);
BER encoding is used in LDAP, Certificates, and is commonplace in many other formats.
I'll be happy with information telling me how to Encode or Decode on this class. There is nothing on Stack Overflow or the first few pages of Google (or Bing) regarding this.
Question
How do I convert the byte array above to the corresponding OID using BER decoding?
How can I parse (or attempt to parse) SubjectPublicKeyInfo ASN.1 data in DER or BER format?
It seems the DER encoding\decoding classes are internal to the .NET framework. If so, where are they? (I'd like to ask connect.microsoft.com to make these members public)
How do I convert the byte array above to the corresponding OID using BER decoding?
After you have extracted the OID byte array, you can convert it to an OID string using OidByteArrayToString(). I have included the code below, since I couldn't find a similar function in the .NET libraries.
How can I parse (or attempt to parse) SubjectPublicKeyInfo ASN.1 data in DER or BER format?
I was not able to find a TLV parser in the .NET SDK either. Below is an implementation of a BER TLV parser, BerTlv. Since DER is a subset of BER, parsing will work the same way. Given a BER-TLV byte[] array, it will return a list of BerTlv objects that support access of sub TLVs.
It seems the DER encoding\decoding classes are internal to the .NET framework. If so, where are they? (I'd like to ask connect.microsoft.com to make these members public)
Maybe somebody else can answer this question.
Summary
Here is an example of how you can use the code provided below. I have used the public key data you provided in your previous post. The BerTlv should probably be augmented to support querying like BerTlv.getValue(rootTlvs, '/30/30/06');.
public static void Main(string[] args)
{
string pubkey = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDrEee0Ri4Juz+QfiWYui/E9UGSXau/2P8LjnTD8V4Unn+2FAZVGE3kL23bzeoULYv4PeleB3gfmJiDJOKU3Ns5L4KJAUUHjFwDebt0NP+sBK0VKeTATL2Yr/S3bT/xhy+1xtj4RkdV7fVxTn56Lb4udUnwuxK4V5b5PdOKj/+XcwIDAQAB";
byte[] pubkeyByteArray = Convert.FromBase64String(pubkey);
List<BerTlv> rootTlvs = BerTlv.parseTlv(pubkeyByteArray);
BerTlv firstTlv = rootTlvs.Where(tlv => tlv.Tag == 0x30).First();//first sequence (tag 30)
BerTlv secondTlv = firstTlv.SubTlv.Where(tlv => tlv.Tag == 0x30).First();//second sequence (tag 30)
BerTlv oid = secondTlv.SubTlv.Where(tlv => tlv.Tag == 0x06).First();//OID tag (tag 30)
string strOid = OidByteArrayToString(oid.Value);
Console.WriteLine(strOid);
}
Output:
1.2.840.113549.1.1.1
OID Encode/Decode
public static byte[] OidStringToByteArray(string oid)
{
string[] split = oid.Split('.');
List<byte> retVal = new List<byte>();
//root arc
if (split.Length > 0)
retVal.Add((byte)(Convert.ToInt32(split[0])*40));
//first arc
if (split.Length > 1)
retVal[0] += Convert.ToByte(split[1]);
//subsequent arcs
for (int i = 2; i < split.Length; i++)
{
int arc_value = Convert.ToInt32(split[i]);
Stack<byte> bytes = new Stack<byte>();
while (arc_value != 0)
{
byte val = (byte) ((arc_value & 0x7F) | (bytes.Count == 0 ? 0x0:0x80));
arc_value >>= 7;
bytes.Push(val);
}
retVal.AddRange(bytes);
}
return retVal.ToArray();
}
public static string OidByteArrayToString(byte[] oid)
{
StringBuilder retVal = new StringBuilder();
//first byte
if (oid.Length > 0)
retVal.Append(String.Format("{0}.{1}", oid[0] / 40, oid[0] % 40));
// subsequent bytes
int current_arc = 0;
for (int i = 1; i < oid.Length; i++)
{
current_arc = (current_arc <<= 7) | oid[i] & 0x7F;
//check if last byte of arc value
if ((oid[i] & 0x80) == 0)
{
retVal.Append('.');
retVal.Append(Convert.ToString(current_arc));
current_arc = 0;
}
}
return retVal.ToString();
}
BER-TLV Parser
class BerTlv
{
private int tag;
private int length;
private int valueOffset;
private byte[] rawData;
private List<BerTlv> subTlv;
private BerTlv(int tag, int length, int valueOffset, byte[] rawData)
{
this.tag = tag;
this.length = length;
this.valueOffset = valueOffset;
this.rawData = rawData;
this.subTlv = new List<BerTlv>();
}
public int Tag
{
get { return tag; }
}
public byte[] RawData
{
get { return rawData; }
}
public byte[] Value
{
get
{
byte[] result = new byte[length];
Array.Copy(rawData, valueOffset, result, 0, length);
return result;
}
}
public List<BerTlv> SubTlv
{
get { return subTlv; }
}
public static List<BerTlv> parseTlv(byte[] rawTlv)
{
List<BerTlv> result = new List<BerTlv>();
parseTlv(rawTlv, result);
return result;
}
private static void parseTlv(byte[] rawTlv, List<BerTlv> result)
{
for (int i = 0, start=0; i < rawTlv.Length; start=i)
{
//parse Tag
bool constructed_tlv = (rawTlv[i] & 0x20) != 0;
bool more_bytes = (rawTlv[i] & 0x1F) == 0x1F;
while (more_bytes && (rawTlv[++i] & 0x80) != 0) ;
i++;
int tag = Util.getInt(rawTlv, start, i-start);
//parse Length
bool multiByte_Length = (rawTlv[i] & 0x80) != 0;
int length = multiByte_Length ? Util.getInt(rawTlv, i+1, rawTlv[i] & 0x1F) : rawTlv[i];
i = multiByte_Length ? i + (rawTlv[i] & 0x1F) + 1: i + 1;
i += length;
byte[] rawData = new byte[i - start];
Array.Copy(rawTlv, start, rawData, 0, i - start);
BerTlv tlv = new BerTlv(tag, length, i - length, rawData);
result.Add(tlv);
if (constructed_tlv)
parseTlv(tlv.Value, tlv.subTlv);
}
}
}
Here is a utility class that contains some functions used in the class above. It is included for the sake of clarity how it works.
class Util
{
public static string getHexString(byte[] arr)
{
StringBuilder sb = new StringBuilder(arr.Length * 2);
foreach (byte b in arr)
{
sb.AppendFormat("{0:X2}", b);
}
return sb.ToString();
}
public static byte[] getBytes(String str)
{
byte[] result = new byte[str.Length >> 1];
for (int i = 0; i < result.Length; i++)
{
result[i] = (byte)Convert.ToInt32(str.Substring(i * 2, 2), 16);
}
return result;
}
public static int getInt(byte[] data, int offset, int length)
{
int result = 0;
for (int i = 0; i < length; i++)
{
result = (result << 8) | data[offset + i];
}
return result;
}
}