Manuel Prochnow

Hello Coder

== is not suitable for comparing string. The right way to compare two strings is the equals method.
as not s1 == s2 but s1.equals (s2).

public class Test { public static void main(String[] args) { String s1 = "Superman"; String s2 = "Superman" + ""; System.out.println("s1 == s2 -> " + (s1 == s2)); System.out.println("s1.equals(s2) -> " + s1.equals(s2)); String s3 = ""; String s4 = "Superman" + s3; System.out.println("s1 == s4 -> " + (s1 == s4)); System.out.println("s1.equals(s4) -> " + s1.equals(s4)); } }


regards kiuziu

Knute Snortum wrote:Yes, but your method returns true with a parameter of 1, -1, or the opposite of any prime number.
public class PrimeNumberTest { public static void main(String[] args) { System.out.println("-1 is prime: " + isPrime(-1)); // prints true System.out.println("1 is prime: " + isPrime(1)); // print true System.out.println("-3 is prime: " + isPrime(-3)); // print true } /** * isPrime(number) return true if number is a prime-number * @param number * @return true if prime else false */ public static boolean isPrime(long number) {    if (number == 2 || number == 3) return true;    if (number % 2 == 0 || number < 2) return false; // <-- now work´s fine    long sqrt = (long) Math.sqrt(number) + 1;    for (long i = 3; i < sqrt; i += 2) if (number % i == 0) return false;    return true; } }

thank you for the hint.

Campbell Ritchie wrote:What about negative numbers, 0 and 1?

please check the wikipedia for definition

definition of prime numbers

you find prime numbers starts with 2. that the smalest prime number.

this is my java code for testing of the prime numbers:

/** * isPrime(number) return true if number is a prime-number * @param number * @return true if prime else false */ public static boolean isPrime(long number) {    if (number == 2 || number == 3) return true;    if (number % 2 == 0) return false;    long sqrt = (long) Math.sqrt(number) + 1;    for (long i = 3; i < sqrt; i += 2) if (number % i == 0) return false;    return true; }

It's my pleasure when you use it in your programs

thanks for the hint. Here is my revised contribution.

package coderanch; import java.util.*; public class Program {   public static void main(String[] args) {       String[] os = new String[] {"Mac", "Linux", "Windows"};       printArray(os);       Arrays.sort(os);       printArray(os);       System.out.println(Arrays.binarySearch(os,"Mac")); // with the correct spelling       System.out.println(Arrays.binarySearch(os,"MAc")); // with the erroneous spelling (MAc instead of Mac)   }     public static void printArray(String[] a){       String result = "[";       for(int i = 0; i < a.length; i++){           result += a[i] + ",";       }       result = result.substring(0,result.length() - 1) + "]";       System.out.println(result);   } }

the results are:
[Mac,Linux,Window]  (the array bevor sort)
[Linux,Mac,Window]  (the array after sort)
1                             (the result of binarySearch with the correct spelling)
-2                            (the result of binarySearch with the erroneous spelling (MAc instead of Mac) )

import java.util.*;

public class Program
{
   public static void main(String[] args) {
       String[] os = new String[] {"Mac", "Linux", "Windows"};
       printArray(os);
       Arrays.sort(os);
       printArray(os); System.out.println(Arrays.binarySearch(os,"Mac"));
   }
   
   public static void printArray(String[] a){
       String result = "[";
       for(int i = 0; i < a.length; i++){
           result += a[i] + ",";
       }
       result = result.substring(0,result.length() - 2) + "]";
       System.out.println(result);
   }
}

Please check the code above to understand the function.

if you don't know what youre code do please don't code something ...

because if you code "classik" or you are code functional, when you not understand how the code works you program never run.

this is my opinion

look at the errror corection at lines 21, 29, 35

I think now your code run

import java.io.*; public class filee { public static void main(String[] args) { char c[] = new char[200]; File d2 = new File("mydirectory2"); d2.mkdir(); File f1 = new File(d2, "file3.txt"); try { f1.createNewFile(); PrintWriter pw = new PrintWriter(f1); FileReader fr = new FileReader(f1); pw.write("Hello\nFolks\nHow are youuuuu?"); // In the file created on the disk, all the words are wirtten // together 'HelloFolksHowareyouuuuuu' and the \n isn't shown in // description pw.flush(); pw.close(); BufferedReader br = new BufferedReader(fr); String s;  // <<<<<<<<<<< int lineNumber = 1; while ((s = br.readLine()) != null) { // s is not declared System.out.println("text in line " + lineNumber++ + ": " + s); } fr.close(); fr = new FileReader(f1);  //  <<<<<<<<<<<<<<<<<<<<<< int size = fr.read(c); System.out.println("the value of size is: " + size); // what is the value of size? if (size > 0) { for (char ch : c) System.out.print(ch); // <<<<<<<<<<<<<<<<<<<<< } fr.close(); } catch (IOException e) { System.out.println(e); } } }

please look at my comments in the code: <<<<<<<<<<<<

Karla Carr wrote:
import java.io.*; class filee { public static void main(String[] args) { char c[] = new char[200]; File d2 = new File("mydirectory2"); d2.mkdir(); File f1 = new File(d2, "file3.txt"); try { f1.createNewFile(); PrintWriter pw = new PrintWriter(f1); FileReader fr = new FileReader(f1); pw.write("Hello\nFolks\nHowareyouuuuu?"); //In the file created on the disk, all the words are wirtten together 'HelloFolksHowareyouuuuuu' and the \n isn't shown in description pw.flush(); pw.close(); BufferedReader br = new BufferedReader(fr); while((s=br.readLine())!=null)  //  <<<<<<<  s is not declared !!!!!!!!!!!!!!!!!! { System.out.println(s); }            int size = fr.read(c);   //  <<<<<<<<<<<  what is the value of size ??  take a look a the documentation !! for(char ch: c) System.out.println(ch); //Nothing gets printed!! Why so?? fr.close();        } catch(IOException e) { System.out.println(e); } } }

My other question is when I type out pw.close() then does it also imply br.close() or fr.close() has also been done? (Other questions are in comments in the code)

Hello ShinRyu Kazuto,

Please take a look at this code it´s more easier but dont crashed and you can read a text-file and show it (I think it ...)

import java.io.File; import java.io.IOException; import java.util.Scanner; import javafx.application.Application; import javafx.scene.Scene; import javafx.scene.control.Label; import javafx.scene.control.Menu; import javafx.scene.control.MenuBar; import javafx.scene.control.MenuItem; import javafx.scene.control.TextArea; import javafx.scene.layout.BorderPane; import javafx.stage.FileChooser; import javafx.stage.Stage; public class IO extends Application { public static void main(String[] args) { launch(args); } @Override public void start(Stage primaryStage) throws Exception { double width = 480; double height = 300; // BorderPane for Menu in Top-Area and text in Center-Area BorderPane root = new BorderPane(); final TextArea textArea = new TextArea(); textArea.setWrapText(true); // adding menu MenuBar mainMenu = new MenuBar(); Menu menu= new Menu("File"); MenuItem open = new MenuItem("Open"); MenuItem save = new MenuItem("Save"); menu.getItems().addAll(open, save); mainMenu.getMenus().addAll(menu); root.setTop(mainMenu); root.setCenter(textArea); root.setBottom(new Label("manuel")); open.setOnAction(x -> { FileChooser fc = new FileChooser(); File file = fc.showOpenDialog(primaryStage); if (file != null) { try { Scanner fin = new Scanner(file); while (fin.hasNext()) { // read from the file, appending text to a control or other object textArea.setText(textArea.getText() + fin.nextLine() + "\n"); } fin.close(); } catch (IOException e) { System.out.println(e); } } }); save.setOnAction(x -> { FileChooser fc = new FileChooser(); File file = fc.showSaveDialog(primaryStage); if (file != null) { // here seve the data to file } }); // Set up stage and scene Scene scene = new Scene(root, width, height); primaryStage.setScene(scene); primaryStage.setTitle("Text Area"); primaryStage.show(); } }

Knute Snortum wrote:I'm not familiar with this class.  Where did you see it?  Why do you need it?  

at the java code in the post at:

File Scanner with java.lang.nullpointer error?File Sanner with java.lang.nullpointer error?

there was used this module: p1utils

I  am looking for this in google search, but I found nothing matched.


Thanks for help   ;-)

Knute Snortum wrote:Manuel Prochnow,
Your post was moved to a new topic.
(This informational message will self destruct in two days)

I am new here. why my post was moved?

my post was writen foer the topic

"File Scanner with java.lang.nullpointer error?"

Hello

import p1utils.FileScanner;

the module is unknown to me. Where can I find this?

thanks for answer