Shall I avoid Exclamation Mark(!) in If-Statement in Java

Today I read a post that we should not use "!" in If statement in order to gain a better Perfermance. Because the "!" operator adds extra action for your program. It sounds not a good idea. Is it really truth?

I did a simple experiment.

I wrote 2 Java snippets:

// App.java
public final class App {
public static void main(String[] args) {
if(App.shouldPrintMessage()) {
System.out.println("Hello, wolrd");
}
}
public static boolean shouldPrintMessage() {
return true;
}
}

Ran javac App.java and then I got App.class. Ran javap -c App.class to view the bytecode.

Here it is:

public final class App {
public App();
Code:
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]);
Code:
0: invokestatic #2 // Method shouldPrintMessage:()Z
3: ifeq 14 // If-Equal !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
6: getstatic #3 // Field java/lang/System.out:Ljava/io/PrintStream;
9: ldc #4 // String Hello, wolrd
11: invokevirtual #5 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
14: return
public static boolean shouldPrintMessage();
Code:
0: iconst_1
1: ireturn
}

And then I added ! in If-Statement

public final class App {
public static void main(String[] args) {
if(!App.shouldPrintMessage()) {
System.out.println("Hello, wolrd");
}
}
public static boolean shouldPrintMessage() {
return true;
}
}

Checked the bytecode

public final class App {
public App();
Code:
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]);
Code:
0: invokestatic #2 // Method shouldPrintMessage:()Z
3: ifne 14 // If-Not-Equal !!!!!!!!!!!!!!!!!!!!!!!!!!!!!
6: getstatic #3 // Field java/lang/System.out:Ljava/io/PrintStream;
9: ldc #4 // String Hello, wolrd
11: invokevirtual #5 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
14: return
public static boolean shouldPrintMessage();
Code:
0: iconst_1
1: ireturn
}

As you can see, the main difference is the ifeq and the ifne.

Let me tried the example exactly provided in the post I read.

public final class App {
public static void main(String[] args) {
int a = 2;
if(!(a <= 1)) {
System.out.println("Hello, wolrd");
}
}
}
// vs
public final class App {
public static void main(String[] args) {
int a = 2;
if(a > 1) {
System.out.println("Hello, wolrd");
}
}
}

And here is the output

public final class App {
public App();
Code:
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]);
Code:
0: iconst_2
1: istore_1
2: iload_1
3: iconst_1
4: if_icmple 15
7: getstatic #2 // Field java/lang/System.out:Ljava/io/PrintStream;
10: ldc #3 // String Hello, wolrd
12: invokevirtual #4 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
15: return
}
// vs
public final class App {
public App();
Code:
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]);
Code:
0: iconst_2
1: istore_1
2: iload_1
3: iconst_1
4: if_icmple 15
7: getstatic #2 // Field java/lang/System.out:Ljava/io/PrintStream;
10: ldc #3 // String Hello, wolrd
12: invokevirtual #4 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
15: return
}

They're exactly the same in bytecode level.

Two examples showed us that there is NO addtional operation even though we use "!" in If-Statement. And futhermore, don't forget we have runtime optimazation in Java. In 2019, I quite believe the JVM is smart enough to resolve this problem. So I think we can choose whatever we want in If-Statement from the readability perspective.