CODEWITHSUNDEEP
javamemory-management
hawkeye
hawkeye

Reputation: 35692

Finding memory consumed for an operation in Java

Suppose I do a bubble sort example like the following in Java:

package testing;

public class bubbleSort {
public static void main(String a[]) {
    int i;
    int array[] = { 12, 9, 4, 99, 120, 1, 3, 10 };
    System.out.println("Values Before the sort:\n");
    for (i = 0; i < array.length; i++)
        System.out.print(array[i] + "  ");
    System.out.println();
    bubble_srt(array, array.length);
    System.out.print("Values after the sort:\n");
    for (i = 0; i < array.length; i++)
        System.out.print(array[i] + "  ");
    System.out.println();
    System.out.println("PAUSE");
}

public static void bubble_srt(int a[], int n) {
    int i, j, t = 0;
    for (i = 0; i < n; i++) {
        for (j = 1; j < (n - i); j++) {
            if (a[j - 1] > a[j]) {
                t = a[j - 1];
                a[j - 1] = a[j];
                a[j] = t;
            }
        }
    }
}
}

Is there a way to find out

(a) How much RAM the data structure for the array of elements consumes?

(b) If not - is there a way to compare how much RAM that process consumes compared to a vanilla HelloWorld?

package testing;

public class Testing {
public static void main(String[] args) {
    System.out.println("Hello World!");
}

}

Upvotes: 2

Views: 131

Answers (4)

Sai Ye Yan Naing Aye
Sai Ye Yan Naing Aye

Reputation: 6738

Use this formula;

     static long memoryUsed() {
        return runtime.totalMemory() - runtime.freeMemory();
     }

     static final Runtime runtime = Runtime.getRuntime();

Upvotes: 0

AlexR
AlexR

Reputation: 115328

You have to profile your application to get the real memory usage. Try YourKit. Add pause to your application just before calling sort. Create memory snapshot before running the sort and after it finished and compare them.

Calling all GC will not bring you are "real" result. There are a lot of objects allocated by VM itself. The will be probably cleaned and you will get wrong picture.

Upvotes: 0

Manikandan Sigamani
Manikandan Sigamani

Reputation: 1984

You can use getRunTime() to find the runtime of the current program. And totalmemory property will help you find the memory used.

   // Get the Java runtime
    Runtime runtime = Runtime.getRuntime();
    // Run the garbage collector
    runtime.gc();
    // Calculate the used memory
    long memory = runtime.totalMemory() - runtime.freeMemory();

Upvotes: 1

Peter Lawrey
Peter Lawrey

Reputation: 533472

How much RAM the data structure for the array of elements consumes?

Not easily. It will be about 40-48 bytes long, which isn't worth worrying about.

If not - is there a way to compare how much RAM that process consumes compared to a vanilla HelloWorld?

At a guess, I would say your first example uses up to 100 KB more than the second. This is because there is allot going on behind the sense to load extra classes and turn int values into String which is most of the memory consumption. Your array is trivial by comparison.

In any case, 100 KB isn't worth worrying about either. In a desktop 100 KB costs less than 1 cents and is reusable.

Upvotes: 1

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