incomparable types: boolean and null

[Ariana Abrenica]

Can someone help me? Because I have never encountered this error before.

import java.io.*;
public class File{
BufferedReader in;
String read = "a";
public File(){
	try{
	in = new BufferedReader (new FileReader("Sample.txt"));
	while(read == in.readLine()!=null)
	System.out.print("File output" + read);
	in.close();
	}catch (IOException e){
	System.out.print("Error" + e);
	}
}
public static void main(String [] args){
File File = new File();
}
}

[Swastik Dey]

Mismatch in the data type being compared.

[Ariana Abrenica]

Swastik Dey wrote:What is the error?

in line 10 it says incomparable type: boolean and null
while (read == in.readLine()!=null) and it points in "!"

[Swastik Dey]

while((read = in.readLine())!=null)

[Ariana Abrenica]

Swastik Dey wrote:while((read = in.readLine())!=null)

thank you

[Campbell Ritchie]

The reason is the = operator has a lower precedence than ==. You want to read the line first, then check whether it is null, so you need to make the = be evaluated before the == with the additional pair of round brackets ().