FileInputStream文件输入流的资源利用情况

「爱情、让人受尽委屈。」 2022-12-31 14:23 115阅读 0赞

FileInputStream流读取数据时出现资源浪费的情况：  
①资源不浪费的情况

public class FileInput_Test {
        
        public static void main(String[] args) throws IOException {
        
            InputStream iis=null;
            try {
        
                File f = new File("\\d:\\a.txt");
                iis = new FileInputStream(f);
                byte[] bs = new byte[1024];
                int length = -1;//read()方法的返回值是int，文件没有字符是返回-1；
                while ((length = iis.read(bs, 0, bs.length)) != -1) {
        
    //                System.out.println(length);
                    //把byte数组转换成字符串输出
                    String s = new String(bs,0,length);//如果不加读取到的字符长度length 则会出现资源浪费 以空格的形式出现
                    System.out.print(s);
                }
            }finally {
        
                if(iis!=null){
        
                    iis.close();
                }
            }
        }
    }

运行结果图：光标不能往外滑动  
![光标不能往文字外滑动][20201230102340733.png]

②资源浪费情况：

public class FileInput_Test {
        
        public static void main(String[] args) throws IOException {
        
            InputStream iis=null;
            try {
        
                File f = new File("\\d:\\a.txt");
                iis = new FileInputStream(f);
                byte[] bs = new byte[1024];
    //            int length = -1;
                while ((iis.read(bs, 0, bs.length)) != -1) {
        //当读取的文件为空时，read()返回-1
    //                System.out.println(length);
                    //把byte数组转换成字符串输出
                    String s = new String(bs);//去掉了length作为读取到的字符长度
                    System.out.print(s);
                }
            }finally {
        
                if(iis!=null){
        
                    iis.close();
                }
            }
        }
    }

运行结果图：光标能往字符外滑动  
![光标能往外滑动，造成资源空间浪费][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzQ5MDIyNzU1_size_16_color_FFFFFF_t_70]

[20201230102340733.png]: /images/20221120/7ce172e1ca51424ca0118f36128ff9e9.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzQ5MDIyNzU1_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20201230102847861.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzQ5MDIyNzU1,size_16,color_FFFFFF,t_70