public static void main(String[] args) {
        BufferedReader reader = null;
        try {
            reader = new BufferedReader(new FileReader("D:\\workspace\\test\\src\\test.txt"));
            List<String> lines = new ArrayList<String>();
            while(true){
                String line = reader.readLine();
                if(line == null){
                    break;
                }else if(line.matches("\\s*")){
                    continue;
                }else{
                    if(lines.indexOf(line) == -1){
                        lines.add(line);
                    }
                }
            }
            for(int i = 0; i < lines.size(); i++){
                System.out.println(lines.get(i));
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally{
            if(reader != null){
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

------解决方案--------------------

String str(String source){
StringBuilder result=new StringBuilder();
boolean number=true;
for(char the:source.toCharArray()){
        if(the!='\n'){
        number=true;
        result.appaned(the);
}else if(number){
     result.appaned(the);
     number=false;
}
}
}