Title here
Summary here
Our first example demonstrates the use of arrays in Java. An array is a fixed-size collection of elements of the same type.
public class Arrays {
public static void main(String[] args) {
// Here we create an array 'a' that will hold exactly
// 5 integers. In Java, arrays are zero-indexed.
int[] a = new int[5];
System.out.println("emp: " + java.util.Arrays.toString(a));
// We can set a value at an index using the
// array[index] = value syntax, and get a value with
// array[index].
a[4] = 100;
System.out.println("set: " + java.util.Arrays.toString(a));
System.out.println("get: " + a[4]);
// The length property returns the length of an array.
System.out.println("len: " + a.length);
// Use this syntax to declare and initialize an array
// in one line.
int[] b = {1, 2, 3, 4, 5};
System.out.println("dcl: " + java.util.Arrays.toString(b));
// In Java, you can't use '...' to let the compiler count
// the elements. The size is determined by the initializer.
b = new int[]{1, 2, 3, 4, 5};
System.out.println("dcl: " + java.util.Arrays.toString(b));
// Java doesn't support specifying indices in array initializers
// like Go does. We need to create the array and then assign values.
b = new int[5];
b[0] = 100;
b[3] = 400;
b[4] = 500;
System.out.println("idx: " + java.util.Arrays.toString(b));
// Array types are one-dimensional, but you can
// create multi-dimensional arrays.
int[][] twoD = new int[2][3];
for (int i = 0; i < 2; i++) {
for (int j = 0; j < 3; j++) {
twoD[i][j] = i + j;
}
}
System.out.println("2d: " + java.util.Arrays.deepToString(twoD));
// You can create and initialize multi-dimensional
// arrays at once too.
twoD = new int[][]{
{1, 2, 3},
{4, 5, 6}
};
System.out.println("2d: " + java.util.Arrays.deepToString(twoD));
}
}
When you run this program, you’ll see:
emp: [0, 0, 0, 0, 0]
set: [0, 0, 0, 0, 100]
get: 100
len: 5
dcl: [1, 2, 3, 4, 5]
dcl: [1, 2, 3, 4, 5]
idx: [100, 0, 0, 400, 500]
2d: [[0, 1, 2], [1, 2, 3]]
2d: [[1, 2, 3], [4, 5, 6]]
Note that arrays in Java are printed using square brackets []
when using Arrays.toString()
or Arrays.deepToString()
methods.
In Java, arrays have a fixed size once they’re created. If you need a dynamically-sized array, you should consider using an ArrayList
or other collections from the Java Collections Framework.