Java program to Find duplicate elements in an array

public void findDuplicatesInArray()
{
// Find duplicate elements in an array O(n)

Hashtable hashtable=new Hashtable();
int [] inputA={1,2,2,3,4,5,5,6,7};

for(int i=0;i<9;i++)
{
if(hashtable.put(inputA[i], inputA[i])!=null)
{
System.out.println("Duplicate:"+inputA[i]);
}
}



}