java 获取文件大小
java 中如何获取文件的大小呢?
有两种方式
方式一:使用File 的length()方法;
方式二:使用FileInputStream的available()方法;
实例:
@Test public void test01() throws IOException { String filepath = "d:\\bin\\pushpoxy-0.0.1-SNAPSHOT.jar"; System.out.println("File has " + new File(filepath).length()+ " bytes"); FileInputStream fis = null; fis = new FileInputStream(filepath); System.out.println("File has " + fis.available() + " bytes"); }
运行结果 :
File has 29061936 bytes
File has 29061936 bytes
其实这两个方法时有区别的;
File 的length()方法 是获取文件所占硬盘空间大小;
FileInputStream的available()方法是还有多少字节可以读取.
available()方法的说明如下:
Returns an estimate of the number of remaining bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. The next invocation might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.
我们把上面的程序稍微修改一下:
@Test public void test01() throws IOException { String filepath = "d:\\bin\\pushpoxy-0.0.1-SNAPSHOT.jar"; System.out.println("File has " + new File(filepath).length()+ " bytes"); FileInputStream fis = null; fis = new FileInputStream(filepath); byte[]bytes=new byte[10]; fis.read(bytes); System.out.println("File has " + fis.available() + " bytes"); fis.skip(-10); System.out.println("File has " + fis.available() + " bytes"); }
执行结果如下:
File has 29061936 bytes
File has 29061926 bytes
File has 29061936 bytes
总结:获取文件大小时建议使用File 的length()方法
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