Nokia has its own API, so compiles the NOKIA version of the Nokia in SE WTK. If the code contains Nokia specialized classes such as Fullcanvas, then you must throw the classNotFound exception. To solve this problem, you can integrate the WTK of SE and NOKIA to make it easy to use. First, put the NOKIA / DEVICES / down folder (for example, NOKIA_7210_MIDP_SDK_V1_0) COPY to Sonyericsson / J2ME_SDK / PC_EMULATION / WTK1 / WTKLIB / DEVICES, so that the 7210 simulator can select the drop-down menu in the SE WTK emulator; Then open the Nokia_7210_midp_sdk_v1_0 / lib / classs.zip to add the NOKIA folder inside to the two compressed files: 1. Sonyericsson / J2ME_SDK / PC_EMULATION / WTK1 / WTKLIB / EMPTYAPI.ZIP, file is placed in the COM folder of the compressed file; 2. Sonyericsson / J2ME_SDK / PC_EMULATION / WTK1 / LIB / MIDPAPI.ZIP is also placed in the COM folder. This allows you to use the NOKIA 7210 simulator and compile NOKIA in the Sony Ericsson WTK, and there is no problem with RETROGUARD :)