java bufferedreader问题

Question

br =
new BufferedReader(new FileReader("C:\\Product.java"));
String line = null;
while((br.readLine())!=null){
line = br.readLine();//这里的line放到while条件里为什么不同了？
System.out.println(line);
}
和
br =
new BufferedReader(new FileReader("C:\\Product.java"));
String line = null;
while((line=br.readLine())!=null){
System.out.println(line);
}
为什么不同！！！

Answer 1

import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.File;import java.io.FileReader;import java.io.FileWriter;import java.io.IOException;public class Copy { public static void main(String[] args){ //记得先把s1.txt创建在C盘 File source = new File("c:/s1.txt"); File target = new File("c:/s2.txt"); //如果s2不存在则创建s2 if(!target.exists()){ try { target.createNewFile(); } catch (IOException e) { e.printStackTrace(); } } try { BufferedReader br = new BufferedReader(new FileReader(source)); BufferedWriter bw = new BufferedWriter(new FileWriter(target)); char[] buffer = new char[128]; System.out.println("文件复制开始"); while(br.read(buffer) != -1){ bw.write(buffer); } bw.close(); br.close(); System.out.println("文件复制结束"); } catch (Exception e) { e.printStackTrace(); } }}

Answer 2

line = br.readLine();//这里的line在while每次循环时都会被赋值，
br.readLine(); // 只是读取并没有赋值给 变量 line啊

追问

br.readLine(); // 只是读取并没有赋值给 变量 line啊

有啊！！！
while((br.readLine())!=null){

line = br.readLine();//这里赋值了
System.out.println(line);
}

追答

while((br.readLine())!=null){ //在这读了一遍
line = br.readLine();//在这又读了遍，并赋值给line
System.out.println(line);//隔一行打印一行啊
}