java替换文本相关问题

[公子LV]

题目：
编写一个JAVA程序，将次行块风格的代码转换成行尾块风格
代码如下：

public static void main(String[] args) throws IOException {
		File file = new File("Score.java");	
		if(!file.exists()){
			System.out.println("File does not exists");
			System.exit(1);
		}
		Scanner input = new Scanner(file);	//创建输入输出
		PrintWriter output = new PrintWriter(file);

		StringBuilder code = new StringBuilder();
		while(input.hasNext()){
			System.out.println(1);
			String line = input.nextLine();
			String line2=line.trim();
			if(line2.charAt(0)=='{'){
				code.append(" {");
			}else{
				code.append("\r\n"+line);
			}			
		}
		input.close();
		
		
		output.println(code);
		output.close();
		
		
	}

问题是：这样写代码while(){}块内语句不执行，而如果将input关闭之后再创建文件输出，则能正常进行。代码如下：

public static void main(String[] args) throws IOException {
		File file = new File("Score.java");	
		if(!file.exists()){
			System.out.println("File does not exists");
			System.exit(1);
		}
		Scanner input = new Scanner(file);	
		StringBuilder code = new StringBuilder();
		while(input.hasNext()){
			System.out.println(1);
			String line = input.nextLine();
			String line2=line.trim();
			if(line2.charAt(0)=='{'){
				code.append(" {");
			}else{
				code.append("\r\n"+line);
			}			
		}
		input.close();	

		PrintWriter output = new PrintWriter(file);
		output.println(code);
		output.close();
		
		
	}

这是为什么？
我看的《Java语言程序设计》这本书，上面代码就是创建完文件输入立刻创建文件输出的。

[soton_dolphin]

public class EditFile {
    public static void main(String[] args) throws IOException{
        Deque<String> originalCodes = Files.lines(Paths.get("/Users/max/Documents/bells.java"))
                                    .collect(Collectors.toCollection(ArrayDeque::new));

        Deque<String> modifiedCodes = new ArrayDeque<>();
        String line;
        boolean flag = false;
        while((line = originalCodes.pollLast()) != null ){
            if(line.trim().startsWith("{")){
                flag = true;
                continue;
            }
            modifiedCodes.push(flag? line + "{\n" : line);
            flag = false;
        }

        try(BufferedWriter bw = new BufferedWriter(new FileWriter("/Users/max/Documents/bells_new.java"))){
            while((line =modifiedCodes.pollFirst())!=null){
                bw.write(line + "\n");
            }
            bw.flush();
        }
    }
}