Unresolved compilation problem: username cannot be resolved to a variable

import java.util.*; import java.io.*; import java.math.*; public class Welcome {    public static void main(String[] args) {    Console cons = System.console();    username =  cons.readLine("%s","Username:");    char[] password = cons.readPassword("%s","Password:"); } }

这段代码为什么在eclipse下编会报错，而在命令行模式下没有问题?
eclipse 报错如下:
Exception in thread "main" java.lang.Error: Unresolved compilation problem:
username cannot be resolved to a variable

at Welcome.main(Welcome.java:18)

Console cons = System.console();
if(cons != null){
  String username =  cons.readLine("%s","Username:");
   char[] password = cons.readPassword("%s","Password:");
} 错误在于 username 前面没有类型String。

eclipse使用自有的编译器ecj。

Eclipse的Console不是System.console（）