Question

I was wondering would there be a performance differences while i use logical operators instead of several if statements. I saw a nice link, does this apply to java also?

Answer 1

I just created class like

class Test{
    static java.util.Random r=new java.util.Random();
    boolean test(){
        return r.nextBoolean();
    }
    void test1(){
        if (test() && test() && test())
            System.out.println("3x yes");
    }
    void test2(){
        if (test())
            if (test()) 
                if (test())
                    System.out.println("3x yes");
    }
}

compiled it then decompiled by javap -c Test and got these result

class Test {
  static java.util.Random r;

  Test();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":
()V
       4: return

  boolean test();
    Code:
       0: getstatic     #2                  // Field r:Ljava/util/Random;
       3: invokevirtual #3                  // Method java/util/Random.nextBoole
an:()Z
       6: ireturn

  void test1();
    Code:
       0: aload_0
       1: invokevirtual #4                  // Method test:()Z
       4: ifeq          29
       7: aload_0
       8: invokevirtual #4                  // Method test:()Z
      11: ifeq          29
      14: aload_0
      15: invokevirtual #4                  // Method test:()Z
      18: ifeq          29
      21: getstatic     #5                  // Field java/lang/System.out:Ljava/
io/PrintStream;
      24: ldc           #6                  // String 3x yes
      26: invokevirtual #7                  // Method java/io/PrintStream.printl
n:(Ljava/lang/String;)V
      29: return

  void test2();
    Code:
       0: aload_0
       1: invokevirtual #4                  // Method test:()Z
       4: ifeq          29
       7: aload_0
       8: invokevirtual #4                  // Method test:()Z
      11: ifeq          29
      14: aload_0
      15: invokevirtual #4                  // Method test:()Z
      18: ifeq          29
      21: getstatic     #5                  // Field java/lang/System.out:Ljava/
io/PrintStream;
      24: ldc           #6                  // String 3x yes
      26: invokevirtual #7                  // Method java/io/PrintStream.printl
n:(Ljava/lang/String;)V
      29: return

  static {};
    Code:
       0: new           #8                  // class java/util/Random
       3: dup
       4: invokespecial #9                  // Method java/util/Random."<init>":
()V
       7: putstatic     #2                  // Field r:Ljava/util/Random;
      10: return
}

As you can see bytecodes of test1 and test2 are same, so there is no difference in using

    if (test() && test() && test())

or

    if (test())
        if (test()) 
            if (test())