Avoid Nested Loop

Nested loop gives big impact on performance and some time it make worse if not controlled properly. Need to double think before using the nested loop and try to find some alternative way to handle the same. Even if it is used, it should not go to level three in nested loop.
It is explained in the below code.

public class TestLoop {
public static void main(String s[]) {
long start, end;
int[] a = new int[100000];
int[] b = new int[100000];
start = System.currentTimeMillis();
for (int i = 0; i
}
end = System.currentTimeMillis();
System.out.println(end – start + ” ” + “milli seconds for One Time Loop”);
start = System.currentTimeMillis();
for (int j = 0; j
for (int i = 0; i
}
end = System.currentTimeMillis();
System.out.println(end – start + ” ” + “milli seconds for loop B inside Loop A”);
}
}
Result:
0 milli seconds for One Time Loop
44015 milli seconds for loop B inside Loop A
You can see the above result how it becomes 44015 ms for executing the loop inside the loop. These are figure for just an empty loop. For any process getting invoked inside the nested loop, the time will be exorbitantly increase.. I would suggest you to think before using the nesting loop with large data and try to avoid as much as possible. You could try to change/write a code in such a way that it would minimize the nested loop. It is explained using the below code. In the below code I am trying to match the value in a big array and print the ‘Found match’ on the console.
public class TestLoop {
public static void main(String s[]) {
long start, end; String[] arrFirst = new String[1000000];
String[] arrSecond = { “0”, “1” };
for (int i = 0; i length; i++) {
arrFirst[i] = String.valueOf(i);
}
start = System.currentTimeMillis();
for (int i = 0; i length; i++) {
for (int j = 0; j length; j++) {
if (arrFirst[i].equalsIgnoreCase(arrSecond[j])) {
System.out.println(“Found match”);
}
}
}
end = System.currentTimeMillis();
System.out.println(end – start + ” milli “+ “seconds for “);
start = System.currentTimeMillis();
}
}
Result: 30 ms
As you can see that it iterate the 1000000*2 times to complete the process. Since we know arrSecond having only two values 0 and 1 therefore we could easily minimize the code using below way

public class TestLoop1 {
public static void main(String s[]) {
long start, end;
String[] arrFirst = new String[1000000];
String[] arrSecond = { “0”, “1” };
for (int i = 0; i length; i++) {
arrFirst[i] = String.valueOf(i);
}
start = System.currentTimeMillis();
for (int i = 0; i length; i++) {
if ((arrSecond[0].equalsIgnoreCase(arrFirst[i]))|| (arrSecond[1].equalsIgnoreCase(arrFirst[i]))) {
System.out.println(“Found match”);
}
}
end = System.currentTimeMillis();
System.out.println(end – start + ” milli “+ “seconds for loop”);
}
}

Result: 15 ms

You could see it just iterate 1000000 times just half the above code and performance get improved twice.
I agree that this is not the best example but this would definitely provide you the way how to handle the nested loop

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Java Loop

Loop
Loops provide efficient way for repeating a piece of code as many times as required. Java has three ways to use the loop control structures and these are:

For Loop: The ‘For-Loop’ is used when we know in advance how many iteration is required
While Loop: The while loop is used when we do not know in advance the number of iterations required so each time before entering the loop the condition is checked and if it is true then the loop get executed
Do-While Loop: The do-while loop is always executed at least once and then the condition is checked at the end of the loop. Developer has to avoid using the do-while loop since it marks major bottleneck in the code.

Since loop repeats the piece of code therefore it gives more cause for performance and need to be very careful during the implementation

First Blogging

I heard and many time about blogging and also i used to read the blogging but first time i will be going to write. Really internet is now revolution of human kind some years no one thought about it. I could remember when the internet bubble blast and we though that it is the end of internet.
When i started my career i never believe on internet power i always thought that it could never be successful. But not only me everyone believe.
The technology is changing drastically and its growing exponentially and i could imagine still its just now started.
We could hope that we will see some more wonder in future.