Solved

Can a Variable be populated from another method in another class.

Posted on 2003-11-10
4
168 Views
Last Modified: 2010-08-05
I've ran across something that I've never seen in Java before.  I step throught somebody's code to get a line of data:
public class VendorMaster
{
next = loaddata.getLine(currentLine);
}

public class LoadData
{
public boolean getLine(byte[] line)
{
...
line is populated here
return gotnext;
}

When I step through the code in VendorMaster after executing getLine, currentLine is populated!  I didn't know you can populate a variable in the called method and make its contents visible in the calling class without actually returning it back in "return" statement.  Why is this happening?  Is this safe to implement especially with having multiple threads?  Thanks.
0
Comment
Question by:Mero
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
4 Comments
 
LVL 15

Assisted Solution

by:jimmack
jimmack earned 50 total points
ID: 9716150
currentLine is passed across as a reference to the beginning of the array, so when the LoadData class writes to it, it's writing to the same memory space.

"currentLine" and "line" are referring to the same block of memory.
0
 
LVL 16

Accepted Solution

by:
imladris earned 100 total points
ID: 9716402
Needing a return statement is true for "primitive" variables (int, long, byte, char etc.). Others (arrays or objects) are passed by reference.

Whether this will pose a challenge w.r.t. multiple threads or not depends on "where" the currentLine is. If it is a shared resource (usually or global or member variable) that multiple threads are accessing, you will need to guard its access with syncronization blocks. However, if currentLine is a purely local, temporary, variable located on the stack, then multithreading will have no impact. Each thread has its own stack, after all.
0
 
LVL 15

Expert Comment

by:jimmack
ID: 9716667
Good catch imladris ;-)  I didn't read the last sentence :-(
0
 
LVL 15

Expert Comment

by:jimmack
ID: 9717113
:-)
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
tomcat startup error 5 160
Problem to Alipay 10 92
glassfish admin console 1 45
Java Inharitance subclass/child extends, reference variable from base/parent class 9 67
Are you developing a Java application and want to create Excel Spreadsheets? You have come to the right place, this article will describe how you can create Excel Spreadsheets from a Java Application. For the purposes of this article, I will be u…
Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…
Viewers learn about the “for” loop and how it works in Java. By comparing it to the while loop learned before, viewers can make the transition easily. You will learn about the formatting of the for loop as we write a program that prints even numbers…
Viewers will learn about the different types of variables in Java and how to declare them. Decide the type of variable desired: Put the keyword corresponding to the type of variable in front of the variable name: Use the equal sign to assign a v…
Suggested Courses

739 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question