I am reading each line of th开发者_运维百科e file in the below way
BufferedReader in = new BufferedReader(new FileReader(inFile));
while (null != (line = in.readLine())) {
}
I want to do some validation in the first line and last line alone. Is there any way to check if it's a first line and last line inside the while loop
while (null != (line = in.readLine())) {
if(firstlineoffile) {
}
else if (lastlineoffile) {
}
else
{
}
}
Cool question. I played a bit round it and here's an SSCCE, just copy'n'paste'n'run it.
package com.stackoverflow.q2292917;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
public class Test {
public static void main(String... args) throws IOException {
// Create test file.
File file = new File("/test.txt");
PrintWriter writer = new PrintWriter(file);
writer.println("line 1");
writer.println("line 2");
writer.println("line 3");
writer.println("line 4");
writer.println("line 5");
writer.close();
// Read test file.
BufferedReader reader = null;
try {
reader = new BufferedReader(new FileReader(file));
String next, line = reader.readLine();
for (boolean first = true, last = (line == null); !last; first = false, line = next) {
last = ((next = reader.readLine()) == null);
if (first) {
System.out.println("first line: " + line);
} else if (last) {
System.out.println("last line: " + line);
} else {
System.out.println("normal line: " + line);
}
}
} finally {
if (reader != null) try { reader.close(); } catch (IOException logOrIgnore) {}
}
// Delete test file.
file.delete();
}
}
Output:
first line: line 1 normal line: line 2 normal line: line 3 normal line: line 4 last line: line 5
I however question the readability and interpretability by starters... ;)
String currentLine = in.readLine();
String nextLine = in.readLine();
boolean hasStarted = false;
while(null != currentLine){
if(!hasStarted){
//first line.
hasStarted = true;
}
//all your processing here.
if(null == nextLine){
//last line, cause there's nothing else coming up
}
currentLine = nextLine;
nextLine = in.readLine();
}
if you add a count, and rearrange your code a little, this should work (I haven't tested this so there may be syntax errros):
int count = 0;
String line = in.readLine();
while (line!=null) {
String currLine = line;
if(count==0){
//currLine is the first line
}
line = in.readLine();
if(line==null){
//currLine is the last line
}
if(count>0 && line!=null){
//do something with lines in between
System.out.println(currLine);
}
count++;
}
public class Vomitfirstline {
public static void main(String[] args) {
BufferedReader br = null;
try {
String sCurrentLine;
br = new BufferedReader(new FileReader("Path"));
br.readLine();
{
while ((sCurrentLine = br.readLine()) != null)
System.out.println(sCurrentLine);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (br != null)br.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
Someone might well come up with a more elegant solution than this, but here we go:
boolean isFirstLine = true;
do{
String line = in.readLine();
if(isFirstLine){
//this is the first line
isFirstLine = false;
}
else if(line==null){ //previous line was the last line
in.reset();
line = in.readLine();
//do last line specific stuff
break;
}
else {
//do stuff for lines in between
}
in.mark(100);
}while (line!=null);
I haven't tested this, so there might be minor errors. I haven't sorted out exception handling in this code. readLine()
, mark()
and reset()
throw IOException
and mark()
can also throw IllegalArgumentException
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