Array.length Question

Hello,
I am trying to find out what class array's length attribute comes from and how array is able to use it.
I have been studying the API but cannot find it or work it out.
Thanks,
Harold Clements

Arrays are considered part of the language and are not listed in the API.
But length appears to behave like a public field, mostly.
Have you checked the language spec? It's available free online.

Similar Messages

Quick array length question...

for this part of my code i'm trying to determine the components needed to find the average of my array. I can't seem to find a way to determine the length of my array (how many components it consists of). Every time I keep getting the dereferencing error....I know it's something simple but I just can't seem to get it right. Please help!
int total = 0, mean = 0, length = 0;
for(int j=0; j<i; j++)
total = total + array[j];
System.out.print(array[j]+" ");
System.out.print(total);

Hi Cher,
This length attribute if any array object will give you the number of components I mean number of elements in that array.
array.length; rather than array.length();
This may be helpfull.
int total = 0, mean = 0, length = 0;
for(int j=0; j<array.length; j++)
total = total + array[j];
System.out.print(array[j]+" ");
System.out.print(total);>
Aski

Question on array.Length

I have an array[4]. Then the subscripts are number 0, 1, 2, 3. Does array.Length return 4 or 3. I am thinking 4 but I want to make sure.

java.secure(?).SecureRandom.java.security.SecureRandom
It's more straightforward and has better statistical properties.While I agree, with the straightforward,
but statistical I would of thought they'd
be even.It's better for several reasons:
1) nextInt is faster. It uses (on average) 1-1/3 calls to next(int), whereas nextDouble() (what Math.random() uses) always uses two. This also means nextInt will use up the generator's period more slowly.
2) It's statistically better. Although the odds of you noticing that some numbers are favored (slightly) over the "noise" of the prng's own bias are negligible.
3) It's nicer to use nextInt. It uses OO (instead of the relatively global function call to Math.random()), it doesn't compete with other parts of the Application for using up some of the prng's period, it allows the substitution of other (better or worse) algorithms with fewer changes, and it looks better.
~Cheers

This and super keywords, array.length attribute

'this' and 'super' keywords and array.length attribute are declared in which java class?
and also during running of a java program how they are initialized and how they work?

'this' and 'super' keywords and array.length attribute are declared in which java class?They are not declared in any Java class, any more than the keywords 'class', 'interface', 'for', 'while', etc., are. They are defined in the grammar of the Java language, in the Java Language Specification.
and also during running of a java program how they are initialized and how they work?That's much too large a question for a forum. Try reading the Java Tutorial.

Maximum possible ARRAY LENGTH ?!?!

Hello All
How can I know (before allocating memory) what is the maximum possible array length. Does it depend on the JVM version or OS or something else ???
Please help !

Thanx All !!!
I've moved to more "memory saving" algorithm, so there is no problem now :-))
But another 2 questions has poped up: I'm using a Vector object in a pretty long loop (millions of iterations) and once in a while accumulating some data (Long and Double objects) by adding them to the Vector.
1. What can be the maximum possible vector length ?
2. What's faster: using a Vector object or using a regular "long or double" array that should be reallocated as:
double[] arr = new double[****];
for(long i=0; i<Long.MAX_VALUE; i++)
    // add new elem
    double[] tmp = new double[arr.length+1];
    System.arraycopy(arr, 0, tmp, 0, arr.length);
    tmp[tmp.length] = newElem;
    arr = tmp;
}

Why arrays length is defined to be a field not a method in Java?

Why arrays length is defined to be a field not a method in Java?

TRANSLATE result USING R.
This statement replaces all characters in field result according to the substitution rule stored in field string R . R contains pairs of letters, where the first letter of each pair is replaced by the second letter.
in your case TRANSLATE result USING '#'.
menas '#' and ' ' space are 2 pair of characters.. and # is replaced by ' ' (space).
for better understanding..
Example:
DATA: T(10) VALUE 'AbCdEfGhIj',
STRING LIKE T,
RULE(20) VALUE 'AxbXCydYEzfZ'.
STRING = T.
TRANSLATE STRING USING RULE.
WRITE / STRING.
Output:
xXyYzZGhIj
Hope this helps..

How to set array length correctly in this case

class RunJavaCode implements ActionListener{
    public void actionPerformed(ActionEvent e){
      try{
        Process proc=Runtime.getRuntime().exec("java javaapp");
        InputStream input=proc.getInputStream();
        byte[] b=new byte[3000];
        input.read(b);
        String javaReport=new String(b);
        input.close();
        outputText.setText(javaReport);
      }catch(IOException ioex){System.out.println("IOException is "+ioex);}
}how to set this array(byte[] b) length correctly? I mean this array length should not only save memory,but also enough to use('enough to use' mean that read outputed info from console to this byte array never overflow)

Hi,
you cannot know in advance, how many bytes will be read. But the read-method returns the number of bytes actually read and this is important!
So at least you have to write:        int r = input.read(b);
        String javaReport=new String(b, 0, r); However, you still do not know, whether there is even more output available. You could however retrieve the data in a loop and append it e.g. to a StringBuffer, until EOF is encountered.

Maximum array length in javacard

hi all
i have a java class with 20 member variables.
member variables are array of bytes. i doesn't allocate
memory for this variables in class constructor,
memory for this variables is dynamically allocated
in my javacard applet (*runtime*).
i defined an array of this class in my applet( in applet constructor):
myclassArray = new myclass[MAX]
for ( short i =0; i < MAX; i++ )
    myclassArray[i] = new myclass();myclass.java:
       class myclass {
             byte[] membervariable1;
              setVar1( byte[] input) {
               membervariable1 = input;
        }if MAX >= 100 , i can't load applet on the card.
(error :conditions of use not satisfied)
why this problem occurs? my card is 32k and i doesn't allocate memory for myclass member variables in applet constructor;
maybe an array of class in javacard has a maximum value in its length. am i right?
thanks,
siavash

s.fallahdoost wrote:
hi all
i have a java class with 20 member variables.
member variables are array of bytes. i doesn't allocate
memory for this variables in class constructor,It doesn't look like it. If you look at the code snippet below, which is located in the constructor, you are allocating memory in the loop.
memory for this variables is dynamically allocated
in my javacard applet (*runtime*).Does not like it neither. If you look at your second code snippet, you're jusr re-referencing the pointer to another instance.
i defined an array of this class in my applet( in applet constructor):
myclassArray = new myclass[MAX]
for ( short i =0; i < MAX; i++ )
myclassArray[i] = new myclass();myclass.java:
class myclass {
byte[] membervariable1;
setVar1( byte[] input) {
membervariable1 = input;
}if MAX >= 100 , i can't load applet on the card.
(error :conditions of use not satisfied)Could be, since you're allocating memory in the constructor.
why this problem occurs? my card is 32k and i doesn't allocate memory for myclass member variables in applet constructor;
maybe an array of class in javacard has a maximum value in its length. am i right?The maximum array length is 32k.

Problems with getting array length

I couldn't get array length in the java from the oracle.
Here is my source.
Can anybody answer me, I will really appriciate that.
Thanks.
public class Test_tb{
public static double Test (oracle.sql.ARRAY args){
double ret = 0;
try {
Double[] retArr = (Double[]) args.getArray();
return retArr.length;
} catch (Exception e){}
return ret;
}

I've rewritten your code to include the display of any exception that might occur. Could you please run it and post any stack trace here? Thanks.
public class Test_tb{
public static double Test (oracle.sql.ARRAY args){
double ret = 0;
try {
    Double[] retArr = (Double[]) args.getArray();
    return retArr.length;
} catch (Exception e){}
    e.printStackTrace();
    return ret;
}

How to calc array length in Labwindows CVI ?

How to calc array length in Labwindows CVI ? In labwiew,I can find function to calc array length,but in CVI ,I can not ,...

Hello 让一切随风
char *name ;
int length = 0;
int i = 0;
name = malloc(256) ;
strcpy(name , "National Instruments");
while( name[i] ! = "\0")
length ++;
i++
free(name);

Finding Array Length

I was just wondering if i have an array
double [][][] array = new double [1][2][3];array.length only gives 1, what function can i use to find the size of the other dimensions (2 and 3)? Thanks in advance for any help.

I'll try and explain this a little better.
Say array[0].length is 2, then that means that there is only
array[0][0] and array[0][1].
If array[0][0] is 4, then that means that there is only
array[0][0][0], array[0][0][1], array[0][0][2], and array[0][0][3].
The reason i did array[0][0].length and not array[0][1].length
in my other post is because they would both return the same
thing because of the way you declared the array.
When you dodouble[][] array = new double[2][3];this is making it so that array[0].length is 3 and array[1].length is 3.
But if you do this (shown in the previous post)
double[][] aray = {
{ 2.4, 5.6, 6.4 },
{ 1.4 }
}then array[0].length is 3, but array[1].length is 1.
Hope this helps.

Get Type ArrayElement fails if array length is 0

All:
Get<Type>ArrayElement fails if the array length is 0 in 1.4. It seems to work fine in 1.5. I was "googling" and I found this link -- http://e-docs.bea.com/wljrockit/v315/relnotes/relnotes.htm. It mentions that this problem -- The JNI methods GetStringChars and Get<>ArrayElements threw OutOfMemoryError if called with a String or array of zero length -- was fixed in version 3.1.4. What is version 3.1.4 and how does this relate to JDK verions that I get out of java -version.
I will appreciate any pointers.
M.P. Ardhanareeswaran
Oracle USA

Drag and drop within a datagrid is rather an unusual thing to do.
I would suggest your problem lies in choosing to do something which will cause complications.
Hope that helps.
Recent Technet articles: Property List Editing;
Dynamic XAML

Math / array / matrix-question

Hallo everybody,
first of all: it's not a indesignscripting- but general math-javascriptquestion. please be patient
I've got a first (matrixlike-)array (won't change)
var containers = [
'container11', 'container12', 'container13', 'container14', 'container15',
'container21', 'container22', 'container23', 'container24', 'container25',
'container31', 'container32', 'container33', 'container34', 'container35',
'container41', 'container42', 'container43', 'container44', 'container45',
'container51', 'container52', 'container53', 'container54', 'container55'
and I've got a second array:
["container14", "container25", "container34", "container44", "container54"] //this array may contain 3 up to 8 items
My aim is to check if a part of 5 to 3 items of the second array is part of or equal to a row or column of the matrix-like-array.
For example: "container34", "container44", "container54" or "container11", "container12", "container13", "container14" (as part of second array) would be a result I#m looking for. Note: I only want to find the 'biggest charge'!
Hope it's getting clear and one of the math-cracks will have a idea.
Addittional: there's no MUST to work with arrays. I can also store the data to a object or mixture ... and may fill it with numbers instead of strings ...
To get it visible:
https://dl.dropboxusercontent.com/spa/3ftsuc9opmid3j4/Exports/fourWins/fourWins.html
Items can be dragged and dropped. After every dropp the arrays have to be compared ... and I#m searching for a nice and elegant solution
May be someone's interested
Hans

Hi Hans,
Just a quick note although your question is solved.
Provided that your matrix is 5×5 you could easily map any element to a single character in the set { A, B..., Z } (for example).
Then your problem can be reduced to some pattern matching algorithm, that is, finding the longest part of the input string within a 'flat string' that just concatenates the rows and the columns of the search matrix in the form ROW1|ROW2...|COL1|COL2...|COL5
And you can create RegExp on the fly to compute the solution(s) with almost no effort:
const MX_ORDER = 5;
const MIN_MATCH = 3; // We need at least 3 contiguous items
var bestMatrixMatch = function F(/*str[]*/ROWS, /*str*/ND)
// NB: No check is made on ROWS, so make sure you supply
//     MX_ORDER strings, each being MX_ORDER-sized
    // Put in cache some subroutines
    F.RES_TO_STR ||(F.RES_TO_STR = function()
            return localize("'%1' found in %2", this.result, this.location);
    F.ROWS_TO_HS ||(F.ROWS_TO_HS = function(R, C,i,j)
            for( i=0,C=[] ; i < MX_ORDER ; ++i )
            for( C[i]='',j=0 ; j < MX_ORDER ; C[i]+=R[j++][i] );
            return R.concat(C).join('|');
    // Vars
    var haystack = F.ROWS_TO_HS(ROWS),
        candidates = ND &&
            haystack.match( new RegExp('['+ND+']{'+MIN_MATCH+',}','g') ),
        t, p;
    if( !candidates ) return null;
    // Sort the candidates by increasing size
    candidates.sort( function(x,y){return x.length-y.length} );
    // Grab the matches and keep the best
    while( t=candidates.pop() )
        if( 0 > ND.indexOf(t) ) continue;
        p = 1+~~(haystack.indexOf(t)/(1+MX_ORDER));
        return {
            result:   t,
            location: (p<=MX_ORDER)?('Row #'+p):('Col #'+(p-MX_ORDER)),
            toString: F.RES_TO_STR,
    return null;
// =================
// Sample code
// =================
var rows = [
    "ABCDE",
    "FGHIJ",
    "KLMNO",
    "PQRST",
    "UVWXY"
var needle = "EKLMINSX";
// get the result
var result = bestMatrixMatch(rows, needle);
alert(
    "Searching the longest part of '" + needle + "' in:\r\r" +
    ' '+rows.join('\r').split('').join(' ') +
    '\r\r===============\r\r' +
    (result || "No result.")
@+
Marc

Adding arrays - confusing question

I am in the process of writing a java program where I have to add arrays. The question asks:
This program asks you to assume that your computer has the very limited capability of being able to read and write only single-digit integers and to add together two integers consisting of one decimal digit each. Write a program that can read in two integers of up to 40 digits each, add these digits together, and display the result. Test your program using pairs of numbers of varying lengths. You must use arrays in this problem.
I think I understand up to there is says"Write a program that can read in two integers of up to 40 digits each" from there I am lost.
Can anyone help explain what is needed?
This is what i have so far:
import java.util.*;
public class add
    public static void main(String[] args)
      Scanner in = new Scanner(System.in);
      int x = in.nextInt();
      int y = in.nextInt();
        int[] a = {x};
        int[] b = {y};
        int[] ab = new int[a.length + b.length];
        System.arraycopy(a, 0, ab, 0, a.length);
        System.arraycopy(b, 0, ab, a.length, b.length);
        System.out.println(Arrays.toString(ab));
}

Yeh, sorry about that didn't have the time to go ahead and drag some of the code over when I first found this forum, first thing I tried a quick compile and run just to see what problems I'd get and I got this runtime error of: Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 7
     at java.lang.String.charAt(String.java:687)
     at Joseph_Ryan_P2.main(Joseph_Ryan_P2.java:36)
I threw in some print statements to see how far it gets before the error occurs and it seems to be right before the for loop(see code below)
In this program I'm reading in from a text file that will read two numbers from the same line that are seperated by a space and eventually add them, is the best way to do that by using a tokenizer or some sort of space delimiter? Or is there an easier way? If the tokenizer is best how would i go about that I haven't learned too much about them besides the fact that they exist so far.
Thanks for any help you or suggestions you guys can give.
//Joseph_Ryan_P2.java
//Big Integer Program
//Description:
//     Design and implement a BigInteger class that can add and subtract integers with up to 25 digits. Your
//     class should also include methods for input and output of the numbers.
// Must Use Arrays
import java.io.*;               //neccessary imported libraries
import java.util.*;
public class Joseph_Ryan_P2
     public static void main(String[] args)          //the programs main method
          try
               Scanner scan = new Scanner(new File("BigInts")); //Scanner to read in from plaintext file
          String numline = scan.next();
          int x=0;
          int [] big1 = new int [numline.length()];
          System.out.println(numline);
               int [] big2 = new int [numline2.length()];
               String numline2= scan.nextLine();
               System.out.println(numline2);
          for(int i = numline.length() - 1; i >= 0; i++)
          char current = numline.charAt(i);
          int d = (int) current - (int) '0';
               big1[i] = d;
          }//end for loop
          }//end try
          catch(FileNotFoundException exception)
System.out.println("The file could not be found.");
catch(IOException exception)
System.out.println(exception);
} //end catch statements
     }//end main
}//end class

The arrays class question

consider the code below
int[] list = {2, 4, 7, 10};
java.util.Arrays.fill(list, 7);
java.util.Arrarys.fill(list, 1, 3, 8);
System.out.print(java,util.Arrays.equals(list, list));i understand line 2, it gonna fill 7 into the array,so the output would be Line 2: list is {7, 7, 7, 7}
my question is line 3, how come the output would be {7, 8, 8,7} what does 1 and 3 represent in a arrary?
the line 4 output would be {7, 8,8,7} again why?
Thank you guys whoever is gonna take to respond me questions

zerogpm wrote:
but which 2 lists were comparing ? since i have list list with the same name1) You're not comparing lists, you're comparing arrays.
2) You're comparing a single array with itself.
3) Objects, including arrays, do not have names. Classes, variables, and methods have names. Objects do not.

Array.length Question

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