#vulnerable code 
                             @Override
	public void run(ClassGroup group)
	{
		this.group = group;
		group.buildClassGraph();
		
		execution = new Execution(group);
		execution.populateInitialMethods();
		execution.run();
		
		findUses();
		
		Field f = group.findClass("class41").findField("field1170");
		calculate(f);
	} 
                            #location 13 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             @Override
	public void run(ClassGroup group)
	{
		this.group = group;
		group.buildClassGraph();
		
		execution = new Execution(group);
		execution.populateInitialMethods();
		
		Encryption encr = new Encryption();
		execution.setEncryption(encr);
		
		execution.run();
		
		encr.doChange();
		
//		findUses();
//		
//		Field f = group.findClass("class41").findField("field1170");
//		calculate(f);
	}