public class RuntimeDemo
{
    public static void main(String[] args)
    {
        /*
         * Returns the runtime object associated with the
         * current Java application.
         */
        Runtime runtime = Runtime.getRuntime();
        /*
         * Returns the total amount of memory in the Java
         * virtual machine.
         */
        System.out.println("Total Memory: " + runtime.totalMemory());
        /*
         * Returns the amount of free memory in the Java
         * Virtual Machine.Calling the gc method may result
         * in increasing the value returned by freeMemory.
         */
        System.out.println("Free Memory: " + runtime.freeMemory());
        /*
         * Returns the maximum amount of memory that the
         * Java virtual machine will attempt to use.
         */
        System.out.println("max Memory: " + runtime.maxMemory());
    }
}

Total Memory: 112721920
Free Memory: 112134704
max Memory: 1659371520