Arrays
Arrays can be created with new operator, or alternatively with {} syntax.
/**
* One way to create an array is with new operator ...
* which allocates the memory for 3 elements
*
* You can also create and initialize the array with {} syntax
* Array length is the number of elements between braches
*/
package com.minte9.basics.arrays;
public class Arrays {
public static void main(String[] args) {
int[] nums;
nums = new int[2];
nums[0] = 1;
nums[1] = 2;
String[] names = {"John", "Marry", "Ana"};
System.out.println(nums[1]); // 2
System.out.println(names[2]); // Ana
try {
names[3] = "Willy";
} catch (Exception ex) {
System.out.println(ex.getMessage()); // Index 3 out of bounds
}
}
}
Types
An array is forever an array.
/**
* An array is forever an array
*
* Creating an array of Dogs, not a new Dob object
*/
package com.minte9.basics.arrays;
public class Types {
public static void main(String[] args) {
Dog[] dogs = new Dog[4]; // array of Dogs
dogs[0] = new Dog();
dogs[1] = new Dog();
// dogs[2] = 222; // Compiler Error
System.out.println(dogs.length); // 4
}
}
class Dog {}
Join
Starting with Java 8 we can use String.join() method.
/**
* Array string elements can be joined with ...
* String.join() method (since JDK 1.8)
*/
package com.minte9.basics.arrays;
public class Join {
public static void main(String[] args) {
String[] A = new String[] {"a", "b", "c"};
System.out.println(
String.join(", ", A) // a, b, c
);
}
}
Last update: 342 days ago
Questions and answers
In Java an array is always
- a) an object
- b) a collection of values
Dog[] dogs;
- a) creates a new Dog object
- b) creates a new Array
