java 解压文件代码中一个语句不理解解决思路

public static void unzip(String zipFile, String destpath)            throws IOException {        ZipInputStream zis = new ZipInputStream(new FileInputStream(zipFile));        ZipEntry z = null;        while ((z = zis.getNextEntry()) != null) {            if (z.isDirectory()) {                File f = new File(destpath + z.getName());                f.mkdirs();            } else {                String file = z.getName();                FileOutputStream fos = new FileOutputStream(destpath + file);                int tmp = -1;                [color=#FF0000]while ((tmp = zis.read()) != -1) {[/color]                    fos.write(tmp);                }                zis.closeEntry();                fos.close();            }        }    }