java读取文件内容的函数

public static String readFile(String fileName) {
String output = "";

File file = new File(fileName);

if (file.exists()) {
if (file.isFile()) {
try {
BufferedReader input = new BufferedReader(new FileReader(
file));
StringBuffer buffer = new StringBuffer();
String text;

while ((text = input.readLine()) != null)
buffer.append(text + "\n");

output = buffer.toString();
} catch (IOException ioException) {
System.err.println("File Error!");

}
} else if (file.isDirectory()) {
String[] dir = file.list();
output += "Directory contents:\n";

for (int i = 0; i < dir.length; i++) {
output += dir[i] + "\n";
}
}
} else {
System.err.println("Does not exist!");
}
return output;
}

public static void main(String args[]) {
Map ab = new HashMap();
String str = readFile("C:/AbCircuitInfo");
String[] temp=str.split("\\n");
for (int i = 0; i < temp.length; i++) {
ab.put(temp[i].substring(0,temp[i].indexOf(",")), temp[i].substring(temp[i].indexOf(",")+1,temp[i].length()));
}
}