Array *not throwing out of bounds exception

I'm trying to learn about exception handling. I can't seem to get
String[] a = names(scnr); To throw an out of bounds exception when it goes beyond 3 elements. I know, most people hate the out of bounds error and I'm trying to make it happen and for the life of me I cannot figure out what I'm doing wrong. Been at it all day and googled all kinds of stuff. But I cannot seem to find exactly what I'm looking for. So I could use some help and perspective.

So I'm inputting a full string that I'm delimiting (trim and splitting) based on commas and spaces and then the pieces are being stored into an array (String []name), then passed to main to be output with String[] a. So it's not erroring when I go beyond 3 elements no matter how I do it. I can just not display anything beyond a[4]. But that's not really what I'm trying to do. Its my first java class so be gentle haha.

Any suggestions?

 import java.util.*;

public class ReturnArrayExample1  
{  
	public static void main(String args[])
	{  
		Scanner scnr = new Scanner(System.in);
		String[] a = names(scnr);           
		for (int i = 0; i < 3; i++) 
		{
			System.out.println(a[i] + " in index[" + i + "].");
		}
		scnr.close();
	}  

	public static String[] names(Scanner scnr)  
	{  							
		String[] name = new String[3];		// initializing
		boolean run = true;
	do 
	{
		try
		{
		System.out.println("Enter 3 names separated by commas ',':(Example: keith, mark, mike)");
		String rawData = scnr.nextLine();
			if(rawData.isEmpty())
			{
				System.err.println("Nothing was entered!");
				throw new Exception();
			}
			else
			{
				name = rawData.trim().split("[\\s,]+");
				run = false;
			}
		}
		catch(ArrayIndexOutOfBoundsException e)
		{
			System.err.println("Input is out of bounds!\nUnsuccessful!");
		}
		catch(Exception e)
		{
			System.err.println("Invalid entry!\nUnsuccessful!");
		}
	}
	while(run == true);
	
	System.out.println("Successful!");
	scnr.close();
	return name;  
	}  
}

If I understand you correctly, you want to throw an ArrayOutOfBoundsException if the names array does not contain exactly 3 elements. The following code is the same as the one you wrote with an if-statement to do just that.

import java.util.*;
public class ReturnArrayExample1  
{  
public static void main(String args[])
{  
Scanner scnr = new Scanner(System.in);
String[] a = names(scnr);           
for (int i = 0; i < 3; i++) 
{
System.out.println(a[i] + " in index[" + i + "].");
}
scnr.close();
}  
public static String[] names(Scanner scnr)  
{                           
String[] name = new String[3];      // initializing
boolean run = true;
do 
{
try
{
System.out.println("Enter 3 names separated by commas ',':(Example: keith, mark, mike)");
String rawData = scnr.nextLine();
if(rawData.isEmpty())
{
System.err.println("Nothing was entered!");
throw new Exception();
}
else
{
name = rawData.trim().split("[\\s,]+");
if (name.length != 3) {
throw new ArrayIndexOutOfBoundsException();
}
run = false;
}
}
catch(ArrayIndexOutOfBoundsException e)
{
System.err.println("Input is out of bounds!\nUnsuccessful!");
}
catch(Exception e)
{
System.err.println("Invalid entry!\nUnsuccessful!");
}
}
while(run == true);
System.out.println("Successful!");
scnr.close();
return name;  
}  
}

As far as I understand, you are expecting an exception (ArrayIndexOutOfBoundsException) to the thrown at line
name = rawData.trim().split("[\\s,]+");
with an argument that the size of array (name) is fixed to 3, and when if the input is beyond 3 then the exception must be thrown; which is not the case.

The reason is in the way assignment happens in java. When you declare String[] name = new String[3];, then an object is created in java heap and its reference is assigned to variable name which is in stack memory.
And when this line name = rawData.trim().split("[\\s,]+"); gets executed then a new array object is created in heap and the variable name starts pointing to the newly created array object on heap. Note: the old object will get available for garbage collection after some time.
This eventually changes the length of the array variable (name) and you do not get any ArrayIndexOutOfBoundsException.

You can understand this more clearly by printing the object on console, like System.out.println(name); after its initialisation and post its assignment.

I will also suggest you to refer this link (https://books.trinket.io/thinkjava2/chapter7.html#elements) to understand how array are created, initialised and copied etc..

Code with system.out commands (for understanding)

import java.util.Scanner;
public class ReturnArrayExample1 {
public static void main(String args[]) {
Scanner scnr = new Scanner(System.in);
String[] a = names(scnr);
System.out.println("Variable (a) is referring to > " + a);
for (int i = 0; i < 3; i++) {
System.out.println(a[i] + " in index[" + i + "].");
}
scnr.close();
}
public static String[] names(Scanner scnr) {
String[] name = new String[3]; // initializing
System.out.println("Variable (name) is referring to > " + name);
boolean run = true;
do {
try {
System.out.println("Enter 3 names separated by commas ',':(Example: keith, mark, mike)");
String rawData = scnr.nextLine();
if (rawData.isEmpty()) {
System.err.println("Nothing was entered!");
throw new Exception();
} else {
name = rawData.trim().split("[\\s,]+");
System.out.println("Now Variable (name) is referring to > " + name);
run = false;
}
} catch (ArrayIndexOutOfBoundsException e) {
System.err.println("Input is out of bounds!\nUnsuccessful!");
} catch (Exception e) {
System.err.println("Invalid entry!\nUnsuccessful!");
}
} while (run == true);
System.out.println("Successful!");
scnr.close();
return name;
}
}

I you want to throw exception when input is more than 3 then there are many ways to do it. One suggestion from @mohamedmoselhy.com is also decent.

If you want java to throw an ArrayIndexOutOfBoundException you have to preserve the created names instance and let java copy the array into your names array:

    String[] names=new String[3];
String[] rawElements=rawData.trim().split("[\\s,]+");
System.arraycopy(rawElements, 0, names, 0, rawElements.length);

output:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException
at java.lang.System.arraycopy(Native Method)
at stackoverflow.OutOfBound.main(OutOfBound.java:8)