Question

What does Java do with long variables while performing addition?

Wrong version 1:

Vector speeds = ... //whatever, speeds.size() returns 2 long estimated = 1l; long time = speeds.size() + estimated; // time = 21; string concatenation?? 

Wrong version 2:

Vector speeds = ... //whatever, speeds.size() returns 2 long estimated = 1l; long time = estimated + speeds.size(); // time = 12; string concatenation?? 

Correct version:

Vector speeds = ... //whatever, speeds.size() returns 2 long estimated = 1l; long size = speeds.size(); long time = size + estimated; // time = 3; correct 

I don’t get it, why Java concatenate them.

Can anybody help me, why two primitive variables are concatenated?

Greetings, guerda

Answer 1

I suspect you’re not seeing what you think you’re seeing. Java doesn’t do this.

Please try to provide a short but complete program which demonstrates this. Here’s a short but complete program which demonstrates correct behaviour, but with your ‘wrong’ code (i.e. a counterexample).

import java.util.*;  public class Test {     public static void main(String[] args)     {         Vector speeds = new Vector();         speeds.add('x');         speeds.add('y');          long estimated = 1l;         long time = speeds.size() + estimated;         System.out.println(time); // Prints out 3     } }