java - 空指针错误: Can't Find Declaration Cause

Question

在控制台中:

Exception in thread "main" java.lang.NullPointerException at SimulatedReality.main(SimulatedReality.java:25)

第 25 行是“BecomesArray = ReadsLine.toCharArray();”。

在我的代码中，我尝试读取文件并检查其所有字符(或至少前十个字符)以查看是否有值为 1 的字符。我试图这样做是为了在使用一次后重置文档的文本。代码的问题是存在由声明问题引起的空指针错误(或者，至少，这是我听到的)。我找不到这个错误在哪里。请并感谢所有帮助我的人。我是初学者，所以解释最好过于简单。

File SRFile = new File("C:/Users/ThinkingBeing/Documents/SRFile.txt");

    SRFileWriter = new   
            FileWriter("C:/Users/ThinkingBeing/Documents/SRFile.txt");
    if(!SRFile.exists()){
            SRFile.createNewFile();
        SRFileWriter.write("000000");
        System.out.println("File now exists.");
    } else {
    for(int i=0;i<=5;i++){          
    SRFileReader = new BufferedReader(new FileReader(SRFile));      
    ReadsLine = SRFileReader.readLine();
    BecomesArray = ReadsLine.toCharArray(); 
    BasicChar = BecomesArray[i];
    if(BasicChar!='0'){         
        SRFileWriter.write("000000");
        System.out.println("File Off Of Counter. Counter Fixed.");
    }
    }
    SRFileWriter.close();
    SRFileReader.close();
    }

Answer 1

我想我找到了您的问题(请遵循 Java 命名约定)。

SRFileReader = new BufferedReader(new FileReader(SRFile)); // <-- file reader once
ReadsLine = SRFileReader.readLine();
BecomesArray = ReadsLine.toCharArray(); 
FileWriter SRFileWriter = new FileWriter
    ("C:/Users/ThinkingBeing/Documents/SRFile.OUT.txt"); // <-- Don't write to 
                                       // your input file while you're reading it.

for(int i=0;i<(BecomesArray != null) ? BecomesArray.length : 0;i++){
  // SRFileReader = new BufferedReader(new FileReader(SRFile));      
  BasicChar = BecomesArray[i];
  if(!SRFile.exists()||BasicChar=='1'){
    // SRFile.createNewFile(); // <-- Would clear your input file.
    SRFileWriter.write("00BOOYTA"); // <-- which was also your output file.
  }
}
SRFileWriter.close();
SRFileReader.close();