NetBeans has strong ability with in multi-language support.
After installed, it looks like in Simplified Chinese only. In fact, you can easily switch it to English/Japanese version by a little change of shortcut command line. You need not install other package or plugin.
English:
"C:\Program Files\NetBeans 6.1\bin\netbeans.exe" --locale en:US
Japanese:
"C:\Program Files\NetBeans 6.1\bin\netbeans.exe" --locale ja:JA
NetBeans 6.1 Multiple Language Version Downloads in local China server
http://zh-cn.netbeans.org/download/6.1/ml/