How to enable Intellij hot code swap - intellij-idea

Question

Intellij does not seem to be doing basic hot code swap on my installation.
For this code:
public class MainTest {
public void method1() {
System.out.println("Breakpoint here");
}
public void method2() {
System.out.println("Line that will get 24 modified");
}
public static void main(String[] args) {
System.out.println("First print here");
MainTest mainTest = new MainTest();
mainTest.method1();
mainTest.method2();
System.out.println("Line that I do not modify");
}
}
I put a breakpoint on mainTest.method1(); then modify the string at method2(), hit ctrl+s and continue to step by step. Unfortunately the runtime is not updated, old string is being printed. Full stop - compile - run does print the new string. So my conclusion is hot-swap not working.
Is there any settings I need to set to enable hot code swap?
Ubuntu, JDK 1.6
Intellij 10.5 Ultimate (evaluation)

Answer 1

After saving your class while waiting on your breakpoint just recompile your class with Build -> Compile 'MainTest.java' or press Ctrl+Shift+F9 with the standard key bindings.
IntelliJ IDEA will then show a small dialog in which it asks you if you want to reload that class.

Answer 2

After below modifications and enabling hot swap, a change in a Java file took 1-2 seconds of restart time. (Initial start time is around 7 seconds for me).
I hope below method helps...
First, you need to check “Make project automatically” in preferences menu.
To open preferences menu;
you can go to top menu and click;
IntelliJ IDEA -> Preferences
or you can type below shortcut via keyboard;
cmd + option + s
Then, you can check Make project automatically as in below picture;
Secondly, you need to modify compiler.automake.allow.when.app.running registry setting as true.
To open registry, you need to click below keyboard shortcut:
cmd + shift + a
Type registry as in below picture, select Registry, and hit enter button of keyboard;
After Registry window opened, type compiler.automake to see compiler.automake.allow.when.app.running option, and check it as in below picture;
Then, you need to restart IntelliJ to make registry changes work.

Answer 3

There is a Debugger > HotSwap option in intellij 11.

Answer 4

Go to Setting --> Select Debug --> HotSwap

Answer 5

I wanted hotswap to automatically run every time I saved a Java file. None of the other answers did this so I just:
Created a macro that will run on save: https://stackoverflow.com/a/5581992/14731
Added Action: Hotswap at the end of the macro (Run -> Reload Changed Classes)

Answer 6

I think you are asking about this,
Right-click on your java class
Select Compile And Reload File

Answer 7

For anyone experiencing the same problem as me, you might have incurred in the following recent bug affecting the 2020.2 update: https://youtrack.jetbrains.com/issue/IDEA-247530?_ga=2.116305920.729836936.1599654650-984156210.1599654650
TL;DR As a workaround, you need to re-activate the Groovy plugin.

Answer 8

I encountered this problem on Ubuntu. I also had an apparently unrelated issue where IntelliJ gave an error about the file watch limit (my apologies that I no longer have the exact error message). To solve this later issue I did the following steps:
Add the following line to either /etc/sysctl.conf file or a new *.conf file (e.g. idea.conf) under /etc/sysctl.d/ directory:
fs.inotify.max_user_watches = 524288
Then run this command to apply the change:
sudo sysctl -p --system
Now my React components rebuild and hot swap just fine.
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