试图将一个对象写入数组,然后保存到 output.data,然后再次读取对象。
写作:
private void saveBtnActionPerformed(java.awt.event.ActionEvent evt) {
File outFile;
FileOutputStream fStream;
ObjectOutputStream oStream;
try {
outFile = new File("output.data");
fStream = new FileOutputStream(outFile);
oStream = new ObjectOutputStream(fStream);
oStream.writeObject(arr);
JOptionPane.showMessageDialog(null, "File Written Successfully");
oStream.close();
} catch (IOException e) {
System.out.println("Error: " + e);
}
}
阅读:
private void readBtnActionPerformed(java.awt.event.ActionEvent evt) {
File inFile;
FileInputStream fStream;
ObjectInputStream oStream;
try {
inFile = new File("output.data");
fStream = new FileInputStream(inFile);
oStream = new ObjectInputStream(fStream);
//create an array of assessments
ArrayList <Assessment> xList;
xList = (ArrayList<Assessment>)oStream.readObject();
for (Assessment x:xList) {
JOptionPane.showMessageDialog(null, "Name: " + x.getName() + "Type: " + x.getType() + "Weighting: " + x.getWeighting());
}
oStream.close();
} catch (IOException e) {
System.out.println("Error: " + e);
} catch (ClassNotFoundException ex) {
System.out.println("Error: " + ex);
}
}
代码编译得很好,文件本身也保存得很好。但是当我尝试读取文件时没有任何反应,NetBeans 说
“线程“AWT-EventQueue-0”中的异常 java.lang.ClassCastException:[Lnetbeansswingexample.Assessment;无法转换为 java.util.ArrayList”
麻烦的代码行似乎是
xList = (ArrayList<Assessment>)oStream.readObject();
非常感谢任何帮助,谢谢。很抱歉,如果答案很明显,编程很新。
最佳答案
根据您得到的异常,它看起来像 oStream.readObject()
返回一个 Assessment
数组,而不是一个 List
。您可以将其转换为 List
:
List <Assessment> xList;
xList = Arrays.asList((Assessment[])oStream.readObject());
或者如果您必须使用 java.util.ArrayList
:
ArrayList<Assessment> xList;
xList = new ArrayList<> (Arrays.asList((Assessment[])oStream.readObject()));
关于java - 无法转换为 java.util.ArrayList,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/30071072/