CODEWITHSUNDEEP
java
Ambassador
Ambassador

Reputation: 33

Is there a way to assess/measure the efficiency of code in java

for instance, I have two versions of a simple count loop - both achieve the same thing but one is more efficient (and presumably uses less memory) than the other. See below:

CODE 1:

int num;
for (num =0; num<10; num++){
System.out.println(num);
}

CODE 2:

for (int num=0; num<10; num++){
System.out.println(num);
}

Upvotes: 1

Views: 55

Answers (1)

weston
weston

Reputation: 54801

They compile identically and so have identical performance and memory requirements.

For proof look at the compiled java byte code using javap -c <classfile>

Code:

public static void a() {
    for (int num = 0; num < 10; num++) {
        System.out.println(num);
    }
}

public static void b() {
    int num;
    for (num = 0; num < 10; num++) {
        System.out.println(num);
    }
}

Byte code:

public static void a();
Code:
   0: iconst_0      
   1: istore_0      
   2: goto          15
   5: getstatic     #15                 // Field java/lang/System.out:Ljava/io/PrintStream;
   8: iload_0       
   9: invokevirtual #21                 // Method java/io/PrintStream.println:(I)V
  12: iinc          0, 1
  15: iload_0       
  16: bipush        10
  18: if_icmplt     5
  21: return        

public static void b();
Code:
   0: iconst_0      
   1: istore_0      
   2: goto          15
   5: getstatic     #15                 // Field java/lang/System.out:Ljava/io/PrintStream;
   8: iload_0       
   9: invokevirtual #21                 // Method java/io/PrintStream.println:(I)V
  12: iinc          0, 1
  15: iload_0       
  16: bipush        10
  18: if_icmplt     5
  21: return

Upvotes: 3

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