int can't be null, but Integer can. You need to be careful when unboxing null Integers since this can cause a lot of confusion and head scratching!
e.g. this:
int a = object.getA(); // getA returns a null Integer
will give you a NullPointerException, despite object not being null!
To follow up on your question, if you want to indicate the absence of a value, I would investigate java.util.Optional<Integer> or java.util.OptionalInt
int can't be null, but Integer can. You need to be careful when unboxing null Integers since this can cause a lot of confusion and head scratching!
e.g. this:
int a = object.getA(); // getA returns a null Integer
will give you a NullPointerException, despite object not being null!
To follow up on your question, if you want to indicate the absence of a value, I would investigate java.util.Optional<Integer> or java.util.OptionalInt
No. Only object references can be null, not primitives.
That code will give a NullPointerException when you run it. It's basically equivalent to:
Integer a = null;
int b = a.intValue();
... which makes it clearer that it will indeed fail.
You're not really assigning a null value to an int - you're trying and failing.
It's fine to use null as a value for an Integer; indeed often Integer is used instead of int precisely as a "nullable equivalent`.
It is not possible. You will get NullPointerException
Hi! So this is my first time posting on here so sorry if this formating is wrong and it doesn't make much sense. I am working with Java and we have to create 2 Integer variables that store the value null in the beginning. These same variables then need to be used later to get user input and set that as the new value. We were provided with a sample run of what should be outputted. We were also provided with objectives that I put in at the bottom of this post. The issue is that I cannot set Integer a and b to two values. Meaning I cannot have Integer equal null and the user input. However, the parameters set to show me that to get this problem correct it needs to be that way. integer a must equal null and user input. Again I am really sorry if this is the wrong formatting, this is my first time using Reddit! Thanks for helping or attempting too!
Sample run:
null nullEnter values:>7>12Average of 7 and 12 is 9.5
----
MY CODE:
import java.util.Scanner;
public class U2_L7_Activity_Two{
public static void main(String[] args){
Scanner scan = new Scanner(System.in);
Integer a = null;
Integer b = null;
System.out.println(a + " " + b);
System.out.println("Enter values:");
Integer a = scan.nextInt();
Integer b = scan.nextInt();
double avg = (a+b)/2.0;
System.out.println("Average of " + a + " and " + b + " is " + avg);
}
}
Objectives:
Debug the code provided in the starter file so it does the following:
creates two Integer objects a and b, and initializes them as null
prints the values of a and b (should result in the output "null null")
sets a and b to inputs entered by the user
finds the average of the two values and stores this in a Double value
prints a sentence as shown in the sample run with the values of a, b and the average
I am sure you are over-complicating the problem, it is a real simple thing to do. Check the code below:
Integer i = null;
System.out.println(i == null ?"":i);
Use Integer wrapper class instead of primitive
Integer myInt= null;
For object references you can set null.But you cannot to primitives.
You can't. int is a primitive value type - there's no such concept as a null value for int.
You can use null with Integer because that's a class instead of a primitive value.
It's not really clear what your method is trying to achieve, but you simply can't represent null as an int.
In this case, I would avoid using null all together.
Just use -1 as your null
If you need -1 to be an acceptable (not null) value, then use a float instead. Since all your real answers are going to be integers, make your null 0.1
Or, find a value that the x will never be, like Integer.MAX_VALUE or something.
Correct. int is a primitive type, which means that it contains an explicit value (a number from -2^31 to 2^31-1), and not a reference, so it can't be null. If you really need null values, use Integer.
Your array
int[] a
is of primitive type int. Primitives cannot have a null value but instead have a default value of 0. Only objects in java can have null as a value. Primitives include: byte,short,char,int,long,float,double.
Primitive Java integers cannot be null, but the Integer class, which wraps a primitive int can be null. Here is one option to consider:
Integer[] num = new Integer[3];
num[0] = 23;
num[1] = null;
num[2] = 12;
The boxing rules in Java make it fairly easy to use int and Integer interchangeably, most of the time.
In int array all the elements enitialize to 0 whether you have assigned a value or not. its because array is primitive type.
public class HelloWorld{
public static void main(String []args){
System.out.println("Hello World");
int [] a = new int[10];
for(int i=0; i<10; i++)
System.out.println(a[i]+"");
}
}
when you are initialize a Person object, Person is not a primitive type. so person can be null but age cannot be null since age is primitive type