Get Duplicate Objects from an ArrayList of Objects

public class Order {

private String portId;  
private String action;  
private String idType;  
private String id;  
private BigDecimal amount;  


public String getPortId() {  
    return portId;  
}  
public void setPortId(String portId) {  
    this.portId = portId;  
}  
public String getAction() {  
    return action;  
}  
public void setAction(String action) {  
    this.action = action;  
}  
public String getIdType() {  
    return idType;  
}  
public void setIdType(String idType) {  
    this.idType = idType;  
}  
public String getId() {  
    return id;  
}  
public void setId(String id) {  
    this.id = id;  
}  
public BigDecimal getAmount() {  
    return amount;

}

My code:

List<Order> duplicateList = new ArrayList<Order>();
List<Order> nonDuplicateList = new ArrayList<Order>();

Set<Order> set = new HashSet<Order>();
for (Order order : listContainingAllOrders) {
if (!set.add(order)) {
duplicateList.add(order);
} else {
nonDuplicateList.add(order);
}
}

I want to achieve duplicateList and nonDuplicateList .