How to initialize array in java ?
Individual elements of an array are referenced through the array name and through an integer that represents their position in the array. The numbers you use to identify them are known as subscripts or indexes within the array.
Subscripts are consecutive integers starting with 0. Thus the array k above has components k[0], k[1], and k[2]. Since you begin counting at zero there is no k[3], and trying to access it will throw an ArrayIndexOutOfBoundsException. You can use array components wherever you'd use a similarly typed variable that wasn't element of an array. For instance this is how you'd store values in the arrays above:
k[0] = 2;
k[1] = 5;
k[2] = -2;
yt[17] = 7.5f;
names[4] = "Fred";
This step is known as initializing the array or, more precisely, initializing the elements of the array. Sometimes the phrase "initializing the array" is used to mean while you initialize all the elements of the array.
For even medium sized arrays, it's unwieldy to specify each element individually. It is frequent helpful to use for loops to initialize the array. Here is a loop which fills an array along with the squares of the numbers from 0 to 100.
float[] squares;
squares = new float[101];
for (int i=0; i <= 100; i++) {
squares[i] = i*i;
}
Two things you should note about this code fragment:
- Watch the fenceposts! Since array subscripts begin at zero you required 101 components if you need to involved the square of 100.
- While i is an int, it is promoted to a float when it is stored in squares, since squares is declared to be an array of floats.