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public class Hello {    private static final  String LINE_SEPARATOR = System.getProperty("line.separator");//换行    public static void main(String[] args) throws Exception {        FileWriter writer = null;        try{            writer = new FileWriter("d:\\demoIO.txt");            writer.write("abcdedd"+LINE_SEPARATOR+"HELLOWORLD");        }catch (Exception e){            System.out.println(e.toString());        }finally {            if (writer != null){                try{                    writer.close();                }catch (Exception e){                    throw new RuntimeException("关闭失败");                }            }        }    }