In this section we will discuss important point that we should know about arrays in java.

  • Important point :

    • At the time of Declaration of an array we can not specify the size of the array in java.
      int [5] // wrong ...

    • Every array in Java is an object , Hence we can create it by using new operator.
      int a[ ]=new int[5]

    • For every array type corresponding classes are available. These classes are not applicable for Programmer Level.

    • At the time of array Construction/Instantiation compulsory we should specify the size of an array otherwise we will get Compile-Time error.
      int a[ ]=new int[ ];//error

    • we can have array of size= 0 in java
      int a[ ]=new int[0 ]; //correct

    • If we specify size of an array in negative . Then we will get run time Exception saying NegativeArraySizeException .
      int a[ ]=new int[-3 ]; //error-NegativeArraySizeException

    • To specify the size of array in Java , the allowed data types are byte,short,int and char. if we use any other data type then we will get error.
      int a[]=new int['A']//correct


Program for getting Name of Array Class.
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//example of getting the array class
class Example {

    public static void main(String[] args) {
        int a[] = {2, 3, 23, 5};
        String name = a.getClass().getName();
        System.out.println("Name of array a  = " + name);

        double d[] = {1.3, 4.3};
        String nameD = d.getClass().getName();
        System.out.println("Name of array d =" + nameD);

        String sr[] = new String[34];
        String nameS = sr.getClass().getName();
        System.out.println("Name of array sr = " + nameS);

    }
}

Output:

Name of array a  = [I
Name of array d =[D
Name of array sr = [Ljava.lang.String;

What next?

The next topic is length vs length() in java

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