how to take large size array in java

Question

i am new to java and i want to take large input size array in java. but in gives me some Runtime Error - NZEC, I don\'t know about it and i also did some research on this error

Answer 1

Array sizes are limited to int size (i.e. about 2 billion). You're trying to initialize one with long. Either read the size into an int or cast the long with long a[]=new long[(int)n];.

I recommend the former to avoid any subtle bugs.

Answer 2

To have such a large array may be inefficient in the first place. Can this be replaced with a better data structure that will help in your use case. May be the overall problem that is being attacked, if provided can help solve it in a different more efficient way.

Answer 3

As the other answers suggested, array-indexes are int-based, and an array is probably not the right data structure for whatever it is you want to do.

Let's consider memory usage. An array has a 12 byte object header, followed by n * v bytes for the actual data (where n is the array size, and v the size of the type you're storing in it).

For example, let's consider the following array declaration:

long[] longArray = new long[Integer.MAX_VALUE];

A long has 64 bits, or 8 bytes. Integer.MAX_VALUE equals 2147483647. This means your array is going to take 17179869188 bytes, or in other words 17 GB of RAM.

Is it possible to create larger arrays? Definitely: you could make a multi-dimensional array (each additional dimension would multiply the available positions by up to Integer.MAX_VALUE), but the memory usage will be atrocious. Consider the following example:

long[] multiArray = new long[5][5];

This array has 25 positions, so by my earlier formula you might figure it takes 25 * 8 + 12 bytes, or 212 bytes, but a 2-dimensional array is an array of arrays, so each inner array also has an object header, so we're talking (5 * 8 + 12) * 5 + 12 bytes, or 272 bytes. Now imagine doing this on larger levels.

long[] multiArray = new long[Integer.MAX_VALUE][Integer.MAX_VALUE];

This takes (Integer.MAX_VALUE * 8 + 12) * Integer.MAX_VALUE + 12 bytes, or 3.689348813882917e19 bytes (36.89 exabytes, or 36.89 billion GB).

If you really need to work with those amounts of data, you probably need a computing cluster, not an array.

Answer 4

An array index cannot be specified with a long as you have done but only with an int as the array size is limited to Integer max value

But in your case it should not be a problem as Integer max value is 2^31-1. (more than 2 billions) and you requirement is inferior :10^9 (1 billion).
So it should be fine to replace :

   long n=sc.nextLong();// n can be upto 10^9;

by

   int n=sc.nextInt();// n can be upto 10^9;

Answer 5

The size of arrays in Java is of the type int. Since a long can hold more data than an int some data might get lost when converting from long to int.

Answer 6

Array sizes are limited to int size in java. so you need to create your array with int sizes always. you have to take n as int. and replace the long n=sc.nextLong();// n can be upto 10^9; by int n=sc.nextInt();// n can be upto 10^9;

It will work perfectly.