在Java中到达行尾的最后一行

Question

Scanner console = new Scanner(System.in);
String line = "";
String pera = " ";

System.out.println("Enter the text : ");
InputStreamReader isr = new InputStreamReader(System.in);
BufferedReader buf = new BufferedReader(isr);
int lineNum = 0;
do {
    line = buf.readLine();
    System.out.println();
    pera = line + "";
    lineNum++;
    System.out.print(lineNum + " " + pera);
} while (line != null);
isr.close();
buf.close();

input : Hello world I am a file Read me until end-of-file.

output : 1 Hello world 2 I am a file 3 Read me until end-of-file.

and this code output is : 1 Hello world 2 I am a file 3 Read me until end-of-file. 4 null

Answer 1

Let's simplify things. You can assign a variable in a while loop. Read lines one by one in it until it comes to end. We understand this when the BufferedReader reads a null line using (line = br.readLine()) != null .

System.out.println("Enter the text: ");
InputStreamReader isr = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(isr);
int lineNo = 0;
String line;
while ((line = br.readLine()) != null) {
    System.out.println(++lineNo + " " + line);
}
isr.close();
br.close();