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Arrays in Java

Discussion in 'Java' started by pradeep, Aug 5, 2006.

  1. pradeep

    pradeep Team Leader

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    When many items of data of the same class or type have to be stored, it is more efficient to use an array than separate variables or objects.

    For example, if the temperature on each day of the (non-leap) year had to be stored, rather than set up tempjan1, tempjan2... tempdec31 (365 variables) we would use the declaration:

    Code:
    double[] tempArray = new double[ 365 ];
    The array variable tempArray stores 365 doubles, indexed from 0 to 364. Accessing the values in the array is done by using the index as follows:

    Code:
    tempArray[ 0 ] = 0.0;
     lastDay = tempArray[ 364 ];
     
    Normally, arrays are processed using a for loop.

    Example code

    This is the code needed to find the average temperature for the year:

    Code:
    double total=0.0, average;
     int size = tempArray.length;
     for ( int index=0; index < size; index++) {
        total += tempArray [ index ];
     } // end for
     average = total / size;
    The above code uses the attribute ‘length’ of the array variable.

    Initialising an array

    The following line initialises the values and sets the size of an array to represent student grade values:
    Code:
     char[] grades = { 'A', 'B', 'C', 'D', 'E' };
    The array ‘grades’ has 5 elements, each a char(acter).

    Arrays of objects

    Consider

    String[] words = new String[ 25 ];

    The variable words holds 25 String references, but not the Strings themselves, which must be instantiated using ‘new’, eg:

    words[0] = new String ("example text");

    An array can be a formal parameter, as in:

    ... main ( String[] args) {

    which is the method Java uses to pass command line parameter values into a program: args[0], args[1] etc.
     
  2. abcdou

    abcdou New Member

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    hi pradeep!

    how about in two dimensional array?

    The output is:(Table Students)

    Lastname Firstname Address
    abcdou dou philippines

    how to make a code that has a method/function:(two classes)
    1. Assign name
    2.Display name
    3.Search name(What index?)
    4.sort in descending

    pls..............
     
  3. macknonalds

    macknonalds New Member

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    two-dimensional array?

    Its just the same as a simple array, but the difference is that you need to control/manipulate 2 indexes of a certain array; commonly the "i" and "j" indexes... Two-dimensional array do have rows and columns which a certain data can be stored....

    Just follow how pradeep teaches us how to make use of an array, then apply it to a two-dimensional array.....

    <filipino><taga san ka nga pla sa pinas?></filipino>
     

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