Question

我是Java的初学者。＆amp;我一直收到这个错误..指向这一行的java.lang.NullPointerException - ＆gt; Double hOption = healthBenDesig.get（＆＃34; employeeOnly＆＃34;）; 有人可以告诉我，如果我错过了什么或者我究竟做错了什么吗？

private HashMap<String, Double> healthBenDesig;

public VariableList()
    {
      HashMap<String, Double> healthBenDesig = new HashMap<String, Double>();
    }
public VariableList()
    {
      HashMap<String, Double> healthBenDesig = new HashMap<String, Double>();
    }
public void getHMP() 
    {
        Double hOption = healthBenDesig.get("employeeOnly");
        System.out.println("The health Option you chose is: " + hOption);

    }
    public HashMap setHealthOpt()
    {
        healthBenDesig.put("none", 0.00);
        healthBenDesig.put("employeeOnly", 311.87);
        healthBenDesig.put("spouse", 592.56);
        healthBenDesig.put("children", 717.30);
        healthBenDesig.put("kids", 882.60);

        System.out.println(healthBenDesig);
        return healthBenDesig;
    }

Answer 1

您通过在构造函数中重新声明healthBenDesig，使类字段为null，从而隐藏了healthBenDesig。不要重新声明它。

更改

public VariableList() {
    HashMap<String, Double> healthBenDesig = new HashMap<String, Double>();
}

为：

public VariableList() {
    healthBenDesig = new HashMap<String, Double>();
}

Answer 2

您没有初始化您的班级成员healthBenDesig，而是使用lcoal变量对其进行遮蔽。这导致healthBenDesig未初始化并导致NullPointerException。你的构造函数，从

更改它

    public VariableList()
    {
      // re-declaration or shadowing of memeber variable healthBenDesig
      HashMap<String, Double> healthBenDesig = new HashMap<String, Double>();
    }

到

    public VariableList()
    {
        healthBenDesig = new HashMap<String, Double>();
    }

Answer 3

您可以在属性声明

初始化healthBenDesig

private HashMap<String, Double> healthBenDesig = new HashMap<String, Double>();

java.lang.NullPointerException错误

3 个答案: