java - Java中的空指针异常

Question

嗨，我正在尝试在行之间使用“十个破折号”，我想将其写入输出文件。我使用了 writeFile 方法和对象 oDel:oDel.writeFile("----------");

当我写这行时，Eclipse 给了我一个空指针执行。我该怎么办？感谢您的帮助。

public BankSystem(String dataFileName) { 
    this.iDel = new InputDelegate(dataFileName); 
} 

public BankSystem(String inputFileName, String outputFileName, ArrayList personList, ArrayList bankList, ArrayList branchList) { 
    this.iDel = new InputDelegate(inputFileName); 
    this.oDel = new OutputDelegate(outputFileName); 
    this.personList = personList; 
    this.bankList = bankList; 
    this.branchList = branchList;

Answer 1

你实例化了oDel了吗？？ (例如，oDel = new FileWriter(..))??