出现NullPointerException如何解决?

Question

Exception in thread "main" java.lang.NullPointerException
        at java.util.Hashtable.put(Unknown Source)
        at java.awt.GridBagLayout.setConstraints(Unknown Source)
        at addPolicyGUI1.makeComponent(addPolicyGUI1.java:168)
        at addPolicyGUI1.showAddPolicyGUI(addPolicyGUI1.java:133)
        at addPolicyGUI1.<init>(addPolicyGUI1.java:183)
        at addPolicyGUI1.main(addPolicyGUI1.java:186)
是对两个JPanel进行操作时出现的情况

Answer 1

检查makeComponent时是否传进去的是null