Setting/Increase JVM heap size

It is possible to increase heap size allocated by the Java Virtual Machine (JVM) by using command line options.
Following are few options available to change Heap Size.
Xms //set initial Java heap size
-Xmx //set maximum Java heap size
-Xss //set java thread stack size
Java Heap Size(MB)
Minimum Heap 64
Default 128
Maximum 256
Example of Inside Heap : 
public class TestMemory {	
	public static void main(String [] args) {
		int mb = 1024*1024;
		//Getting the runtime reference from system
		Runtime runtime =Runtime.getRuntime();
		System.out.println("##### Heap utilization statistics [MB] #####");
		//Print used memory
        System.out.println("Used Memory:" + (runtime.totalMemory() - 
        	runtime.freeMemory()) / mb);
		//Print free memory
        System.out.println("Free Memory:" + runtime.freeMemory() / mb);
		//Print total available memory
        System.out.println("Total Memory:" + runtime.totalMemory() / mb);
		//Print Maximum available memory
		System.out.println("Max Memory:" + runtime.maxMemory() / mb);
	}
}
OUTPUT
jvm output