jad ( Java Application Discriptor ) 文件是J2ME的一个重要的组成部分，在我们发布J2ME程序的时候，jad文件经常报出各种错误，如：
com.sun.kvem.midletsuite.InvalidJadException: Reason = 13
其中的错误原因是1-52的代码，很让人费解。我在网上找到了这些代码的解释，和大家分享如下：
public static final int JAD_SERVER_NOT_FOUND = 1;
public static final int JAD_NOT_FOUND = 2;
public static final int MISSING_PROVIDER_CERT = 4;
public static final int CORRUPT_PROVIDER_CERT = 5;
public static final int UNKNOWN_CA = 6;
public static final int INVALID_PROVIDER_CERT = 7;
public static final int CORRUPT_SIGNATURE = 8;
public static final int INVALID_SIGNATURE = 9;
public static final int UNSUPPORTED_CERT = 10;
public static final int EXPIRED_PROVIDER_CERT = 11;
public static final int EXPIRED_CA_KEY = 12;
public static final int MISSING_SUITE_NAME = 13;
public static final int MISSING_VENDOR = 14;
public static final int MISSING_VERSION = 15;
public static final int INVALID_VERSION = 16;
public static final int OLD_VERSION = 17;
public static final int MISSING_JAR_URL = 18;
public static final int JAR_SERVER_NOT_FOUND = 19;
public static final int JAR_NOT_FOUND = 20;
public static final int MISSING_JAR_SIZE = 21;
public static final int SUITE_NAME_MISMATCH = 25;
public static final int VERSION_MISMATCH = 26;
public static final int VENDOR_MISMATCH = 27;
public static final int INVALID_KEY = 28;
public static final int INVALID_VALUE = 29;
public static final int INSUFFICIENT_STORAGE = 30;
public static final int JAR_SIZE_MISMATCH = 31;
public static final int NEW_VERSION = 32;
public static final int UNAUTHORIZED = 33;
public static final int JAD_MOVED = 34;
public static final int CANNOT_AUTH = 35;
public static final int CORRUPT_JAR = 36;
public static final int INVALID_JAD_TYPE = 37;
public static final int INVALID_JAR_TYPE = 38;
public static final int ALREADY_INSTALLED = 39;
public static final int DEVICE_INCOMPATIBLE = 40;
public static final int MISSING_CONFIGURATION = 41;
public static final int MISSING_PROFILE = 42;
public static final int INVALID_JAD_URL = 43;
public static final int INVALID_JAR_URL = 44;
public static final int PUSH_DUP_FAILURE = 45;
public static final int PUSH_FORMAT_FAILURE = 46;
public static final int PUSH_PROTO_FAILURE = 47;
public static final int PUSH_CLASS_FAILURE = 48;
public static final int AUTHORIZATION_FAILURE = 49;
public static final int ATTRIBUTE_MISMATCH = 50;
public static final int PROXY_AUTH = 51;
public static final int TRUSTED_OVERWRITE_FAILURE = 52;
有了这些代码的解释，我们就很容易知道错误的原因了。
另外，大家知道，有的手机在安装jar文件的时候，不需要jad文件。这是因为手机厂商在操作系统中内置了对jar文件的解析功能。就如同手机自动生成jad文件，然后使用这个jad文件安装jar文件一样。