Java

How to convert 2d array into 1d array in java

13-Oct-16 21:10

Assuming you actually mean in a command prompt window then it is just a matter of running it via the java command.

Member 1278579110-Oct-16 4:33

10-Oct-16 4:33

class Sort1
{
public static void main(String...avg)
{
int a[][]={{10,50,40},{15,25,10},{25,14,19}};
for(int i=0;i<a.length;i++)
{
for(int j = 0;j<a[i].length;j++)
{
System.out.print(a[i][j]+"\t");
}
System.out.println();
}
int l =a.length;
int b[]=new int[l];
int c=0;
for(int k=0;k<a.length;k++)
{
for(int m=0;m<a[k].length;k++)
{
b[c]=a[k][m];
System.out.print(b[c] +"\t");
c++;
}
}
}
}

Richard MacCutchan10-Oct-16 4:55

10-Oct-16 4:55

Do you have a question?

Member 1278579110-Oct-16 5:35

10-Oct-16 5:35

yeah, i want to know how to calculate the length of 2d array while converting it into 1d array
when i simply used a.length for my 2d array and put it into my 1d array ,then 1d array will print only first column then exception comes Array index out of bound

Richard MacCutchan10-Oct-16 6:12

10-Oct-16 6:12

Well I would guess it is the total number of elements in your 2D array. So it is just a question of adding the number of elements in array[0] + array[1] + ...

Member 1278579110-Oct-16 6:29

10-Oct-16 6:29

yup i got the idea and it works like this
int a[][]={{1,2,3},{4,5,6},{7,2,6}};
int b[] = new int[a.length*a.length];
System.out.print(b.length);
//output is 9
//is this the way of getting length of 2d into 1d array?

Richard MacCutchan10-Oct-16 6:38

10-Oct-16 6:38

What happens if you have something like:

Java

int a[][]={{1,2,3,7,12},{4,5},{7,2,6,9,9,11,22,33,44,55}};

Member 1278579110-Oct-16 6:48

10-Oct-16 6:48

yup in that case my logic isn't working
if you can, please tell me the universal logic for calculating the length while converting 2d array into 1d array

Richard MacCutchan10-Oct-16 7:13

10-Oct-16 7:13

I told you at Re: How to convert 2d array into 1d array in java - Java Discussion Boards[^].

Member 1278579110-Oct-16 7:18

10-Oct-16 7:18

ok i got the answer
thanks buddy for help Smile | :)

Member 1279318014-Oct-16 0:24

Member 12793180

14-Oct-16 0:24

This is showing error

So i solved from my self.....

class Sort1{
public static void main(String...avg)
{
int a[][]={{10,50,40},{15,25,10},{25,14,19}};
int l =a.length;
int b[]=new int[9];
int x=0;
for(int i=0;i<a.length;i++)
{
for(int j = 0;j<a[i].length;j++)
{
System.out.print(a[i][j]+"\t");
b[x]=a[i][j];
x++;
}
System.out.println();
for(int k=0;k<b.length;k++)
{
System.out.print(b[k] +"\t");
}
}
}

Member 1278579115-Oct-16 5:06

Relating Country to its State & Province

15-Oct-16 5:06

Basically i was trying to do bubble sorting in 2d array with logic
first converted 2d array into 1 d array then sort the elements and again converted back that array into 2d array

class Sort1
{
public static void main(String...avg)
{
int a[][]={{1,2,3,7,12},{4,5},{7,2,6,9,9,11,22,33,44,55}};
//System.out.print(a.length);
int totalelements=0;
for(int x=0;x<a.length;x++)
{
for(int y=0;y<a[x].length;y++)
{
totalelements++;
}
}
//System.out.print(totalelements);
System.out.println("\n"+"unsorted 2d array"+"\n");
for(int i=0;i<a.length;i++)
{
for(int j=0;j<a[i].length;j++)
{
System.out.print(a[i][j]+"\t");
}

System.out.println();
}

System.out.println("\n"+"converted 2d array into 1d array"+"\n");
int b[]=new int[totalelements];
//System.out.print(b.length);
int l=b.length;
int c=0;
for(int k=0;k<a.length;k++)
{
for(int m=0;m<a[k].length;m++)
{
b[c]=a[k][m];
System.out.print(b[c] +"\t");
c++;
}
}

for( int i =1; i<=l-1;i++)
{
for(int j=0; j<l-i;j++)
{
if(b[j]>b[j+1])
{
c =b[j];
b[j]=b[j+1];
b[j+1]=c;
}
}
}
int n=0;
for(int i=0 ; i<a.length ; i++)
{
for(int j=0 ; j<a[i].length ; j++)
{
a[i][j] = b[n];
n++;
}
}
System.out.println("\n"+"\n"+"Sorted 2d array "+"\n");
for(int i=0 ; i<a.length ; i++)
{
for(int j=0 ; j<a[i].length ; j++)
{
System.out.print(a[i][j]+" ");
}
System.out.println();
}
}
}

Member 1276860029-Sep-16 23:12

Member 12768600

29-Sep-16 23:12

Hi!

I am currently coding in JSF, but using Java for the back-end beans. Was wondering if anyone is familiar to JSF, to help get a solution or an idea on how I could proceed.

So, if I have a database with 2 tables - Country & State,
but I don't want to have to make a call into the database in order to reduce the resources used. How would I implement in the Java bean a connection between the country and its related states?
Considering that I have the 2 selections in a dropdown menu.

Thanks!

Re: Relating Country to its State & Province

Richard MacCutchan29-Sep-16 23:45

Re: Relating Country to its State & Province

29-Sep-16 23:45

If you do not want to use the database then you need to hold all the data in Lists inside the code, which may be just as expensive.

Member 1276860030-Sep-16 0:17

Member 12768600

30-Sep-16 0:17

And if I make a call to the database, then I'm probably looking to use a couple of for-loops
to go through both tables in my back bean?

Re: Relating Country to its State & Province

Richard MacCutchan30-Sep-16 0:53

compile error: string is private with powershell

30-Sep-16 0:53

Yes, probably. It's a trade off, whichever method you use will have a cost. You need to decide which is the better option for your application.

shoysmTP15-Sep-16 0:53

shoysmTP

15-Sep-16 0:53

a very beginner question...
i'm a newbie in programming... just started java and read about packaging... i created i directory called firstproject and put a directory with one class inside of it and a FirstProject source file in the firstproject directory itself.
i made a class in that package directory that has a private string in it and tried to invoke from FirstProject source file but
getting compile error that the string is private...
i tried changing the string into protected or even public but still getting this error...
this is the class src file...

<pre lang="java">
package stickers;
public class Sticker
{
  private String note;

  Sticker(String note)
  {
    this.note = note;
  }

  public void displayNote()
  {
    System.out.println(note);
  }
}

this is the FirstProject src file...

Java

package firstproject;
import stickers.Sticker;
public class FirstProject
{
  public static void main(String[] args)
  {
    Sticker sticker = new Sticker("hello sticky mehdi");
    sticker.displayNote();
  }
}

this is the actuall error:
error: Sticker(String) is not public in Sticker; cannot be accessed from outside package

Re: compile error: string is private with powershell

Richard MacCutchan15-Sep-16 1:40

Load C++ Library Only Once

15-Sep-16 1:40

You need to make your constructor public so other packages can access it:

Java

public class Sticker
{
  private String note;
 
  public Sticker(String note)
  {
    this.note = note;
  }
// ... etc

I would recommend going to The Java Tutorials[^] and working through them.

Django_Untaken10-Sep-16 9:30

Django_Untaken

10-Sep-16 9:30

Hello there. I have managed to load and use c++ dll using JNI, in my java servlet (System.load). It works perfectly on first request I submit. But on subsequent requests, I get this weir d exception.

java.lang.UnsatisfiedLinkError: Native Library WEB-INF/lib/XXXXXX.dll already loaded in another classloader<br />
        at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1525)

Here is my loading code

public void init(ServletConfig config) throws ServletException 
{
    super.init(config);
    ServletContext context = getServletContext();
    String sMathDllpath = context.getInitParameter("MathDLLPath");	
    System.load(sMathDllpath);

}

I studied this tomcat wiki link and implemented their solution, among others, but could not succeed.
How do I implement it successfully? Thnks for anything you share.

Re: Load C++ Library Only Once

Richard MacCutchan10-Sep-16 20:42

Re: Load C++ Library Only Once

10-Sep-16 20:42

You should declare it as a static action at class level like:

Java

class ... {
    static
    {
        System.loadLibrary("MathDLLPath");
    }
// remainder of your class
}

That will ensure it is loaded when the class is first instantiated, but will only be loaded once.

Django_Untaken11-Sep-16 4:58

Django_Untaken

11-Sep-16 4:58

Richard MacCutchan wrote:
You should declare it as a static action at class level like:

I tried this just now. This is what I have

public class MainServlet extends HttpServlet
{
    static{
	System.loadLibrary("MathDll");
   }

   ......... // rest of the class below this
}

And this is the exception I am getting

<br />
java.lang.UnsatisfiedLinkError: Native Library C:\Program Files\Java\jdk1.7.0_71\bin\MathDll.dll already loaded in another classloader<br />

What am I doing wrong now?

Re: Load C++ Library Only Once

Richard MacCutchan11-Sep-16 6:17