Deadline soon! Give every new object a new attribute value (participants and start numbers) : I'm a beginner in java and working on an assignment. My program is a sports competition with event, participant, team, result and program classes. My deadline is in less than 2 hours and I found a problem during the final testing regarding participants and their start number attribute. 

The participant is given a start number when added. The first gets 100, the next 101, 102 and so on. If participant 102 is removed and a new participant is added, the new one also gets number 102, which appears to be my problem. Apparently these start numbers aren't supposed to be reused. Is there a way to give new participants new start numbers that hasn't been given before? 

From the Participant class:

    private int startNumber;

    public int getStartNumber() {
    		return startNumber;
    	}
    
    	public void setStartNumber(int startNumber) {
    		this.startNumber = startNumber;
    	} 
    + other attributes and methods

From the program class:

    private void addStartNumber(Participant p) {
    		if(allParticipants == null || allParticipants.isEmpty()){
    			p.setStartNumber(100);		
    		}else{
    			p.setStartNumber(findLastStartNumber()+1);
    		}
    			
    	}
    	
    	private int findLastStartNumber(){
    		int lastNumber = 0;
    		
    		for(int i = 0 ; i < allParticipants.size() ; i++){
    			lastNumber = allParticipants.get(allParticipants.size()-1).getStartNumber();
    		}
    		return lastNumber;
    	}