java代码如何从一个文件中读取内容并转换为字符串呢？

实现思路:
    1.借助BufferedReader对象读取文件
    2.将读取出的内容放入StringBuilder字符串中
	采用以上两个步骤，即可完成文本文件中读取内容的操作

private String readFile(String file) throws IOException {
    BufferedReader reader = new BufferedReader(new FileReader (file));
    String         line = null;
    StringBuilder  stringBuilder = new StringBuilder();
    String         ls = System.getProperty("line.separator");

    try {
        while((line = reader.readLine()) != null) {
            stringBuilder.append(line);
            stringBuilder.append(ls);
        }

        return stringBuilder.toString();
    } finally {
        reader.close();
    }
}