How do I remove duplicates from the list- How to remove duplicates from a list?

problem ：

I want to remove duplicates from a list but what I am doing is not working: I want to remove duplicates from the list , But what I did didn't work ：

List<Customer> listCustomer = new ArrayList<Customer>();    for (Customer customer: tmpListCustomer){  if (!listCustomer.contains(customer))   {    listCustomer.add(customer);  } }

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Solution ：

Reference resources ： https://stackoom.com/en/question/BxGs