我无法编译该程序。问题出在最后一行“out.close”。请告诉我如何纠正它以及为什么会导致问题。
import java.io.*;
public class Test {
public static void main(String args[]) throws IOException {
try {
BufferedReader in = new BufferedReader(new FileReader(args[0]));
BufferedWriter out = new BufferedWriter(new FileWriter(args[1]));
String line;
line = in.readLine();
while (line != null) {
out.write(line, 0, line.length());
out.newLine();
line = in.readLine();
}
} finally {
out.close();
}
}
}
最佳答案
你必须在try-finally block 之外声明BufferedWriter out变量,因为try block 中声明的变量超出了finally的范围,称为 block 作用域。代码应该是这样的:
BufferedWriter out = null;
try {
BufferedReader in = new BufferedReader(new FileReader(args[0]));
out = new BufferedWriter(new FileWriter(args[1]));
String line;
line = in.readLine();
while (line != null) {
out.write(line, 0, line.length());
out.newLine();
line = in.readLine();
}
} finally {
if (out != null)
out.close();
}
或者正如评论中所说,如果Java版本是7或更高版本,则应该使用try-with-resources:
try(BufferedReader in = new BufferedReader(new FileReader(args[0]));
BufferedWriter out = new BufferedWriter(new FileWriter(args[1])))
{
String line;
line = in.readLine();
while (line != null) {
out.write(line, 0, line.length());
out.newLine();
line = in.readLine();
}
}
在这种情况下,您不需要在finally block 中手动关闭它。
关于java - 无法关闭输出流,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/32700322/