使用缓存问题

public class CacheManager {  
 
    private static final long MAX_SIZE = 5242880L; // 5MB  
 
    private CacheManager() {  
 
    }  
 
    public static void cacheData(Context context, byte[] data, String name) throws IOException {  
 
        File cacheDir = context.getCacheDir();  
        long size = getDirSize(cacheDir);  
        long newSize = data.length + size;  
 
        if (newSize > MAX_SIZE) {  
            cleanDir(cacheDir, newSize - MAX_SIZE);  
        }  
 
        File file = new File(cacheDir, name);  
        FileOutputStream os = new FileOutputStream(file);  
        try {  
            os.write(data);  
        }  
        finally {  
            os.flush();  
            os.close();  
        }  
    }  
 
    public static byte[] retrieveData(Context context, String name) throws IOException {  
 
        File cacheDir = context.getCacheDir();  
        File file = new File(cacheDir, name);  
 
        if (!file.exists()) {  
            // Data doesn't exist  
            return null;  
        }  
 
        byte[] data = new byte[(int) file.length()];  
        FileInputStream is = new FileInputStream(file);  
        try {  
            is.read(data);  
        }  
        finally {  
            is.close();  
        }  
 
        return data;  
    }  
 
    private static void cleanDir(File dir, long bytes) {  
 
        long bytesDeleted = 0;  
        File[] files = dir.listFiles();  
 
        for (File file : files) {  
            bytesDeleted += file.length();  
            file.delete();  
 
            if (bytesDeleted >= bytes) {  
                break;  
            }  
        }  
    }  
 
    private static long getDirSize(File dir) {  
 
        long size = 0;  
        File[] files = dir.listFiles();  
 
        for (File file : files) {  
            if (file.isFile()) {  
                size += file.length();  
            }  
        }  
 
        return size;  
    }  
}