Introduction to Arrays

One-Dimensional Arrays

A one-dimensional array is a list of similar-typed variables. The general form of a one-dimensional array declaration is:

type var-name[ ];

• type declares the array type.
• type also determines the data type of each array element.

The following declares an array named days with the type "array of int":

int days[];

• days is an array variable.
• The value of days is set to null.

Allocate memory for array

You allocate memory using new and assign it to array variables. new is a special operator that allocates memory. The general form is:

arrayVar = new type[size];

• type specifies the type of data being allocated.
• size specifies the number of elements.
• arrayVar is the array variable.

The following two statements first create an int type array variable and then allocate memory for it to store 12 int type values.

int days[]; 
days = new int[12];

Array creation is a two-step process.

1. declare a variable of the desired array type.
2. allocate the memory using new.

public class Main {
  public static void main(String[] argv) {
    int days[];
    days = new int[12];

    days[1] = 28;

    System.out.println(days[1]);
  }
}

It is possible to combine the declaration of the array variable with the allocation of the array itself.

int month_days[] = new int[12];

Array Element Initialization Values