我是一名新手,正在做一项家庭作业,向我们介绍如何在 Java 中使用文件,并且我正在尝试添加一个选项,以便用户在未成功创建文件时提前退出(例如,如果他们没有写入磁盘的权限)。这是我试图从中结束程序的 try catch block :
// Loop used to repeat try catch block until a file is successfully created/opened
FileWriter FW = null; // Create & initialize the FW object outside of the loop
// to ensure availability in the correct scope
boolean success = false;
while (success == false) {
// Try catch block for handling possible exception thrown by the
// FileWriter constructor
try {
FW = new FileWriter(fileName);
success = true;
}
// Catch allows the user to attempt to rename file and includes option
// to exit program immediately (presumably after multiple failed attempts)
catch (IOException e) {
String failString = "exit";
fileName = (String)JOptionPane.showInputDialog(
"There was an error creating your file. Please\n" +
"ensure you have permission to write to the directory\n" +
"and then re-enter your desired file name. Please do\n" +
"not attempt to specify a directory. Please do not\n" +
"use special characters. Type 'exit' to end the\n" +
"program now.");
if (fileName != failString) {
fileName = fileName + ".txt";
}
else {
JOptionPane.showMessageDialog(null, "Exiting...", "EXITING", 1);
System.exit(0);
}
}
}
我认为应该发生的是,用户将输入术语“退出”作为新文件名,程序将立即退出。但是,当我输入 exit 时,程序只是创建一个名为 exit.txt 的文件并继续执行。我很茫然。
对于哪里出了问题有什么想法或建议更好的方法吗?
最佳答案
使用 equals()
比较字符串,而不是 !=
或 ==
。
所以你需要
if (!fileName .equals(failstring)) {
fileName = fileName + ".txt";
} else {
System.exit(1);
}
有关更多详细信息,请参阅 Java 教程:http://docs.oracle.com/javase/tutorial/java/data/comparestrings.html
顺便说一句:通常使用“积极”表达比使用否定表达更好(人脑能更好地应对它们)。所以推荐使用:
if (fileName .equals(failstring)) {
System.exit(1);
} else {
fileName = fileName + ".txt";
}
相反
关于Java程序根据字符串比较不退出,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/13786197/