How to enable Intellij hot code swap

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...

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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.