IntelliJ switch 语句使用字符串错误:使用 -source 7

I'm trying to use IntelliJ (on Mac OS X) to compile some code I wrote using Eclipse. I've attempted to run the following code:

switch (category) {
    case "below 20":
        below20++;
        break;
    case "20 to 29":
        to30++;
        break;
    case "30 to 39":
        to40++;
        break;
    case "40 to 49":
        to50++;
        break;
    case "50 to 59":
        to60++;
        break;
    case "60 to 69":
        to70++;
        break;
    case "70 t0 79":
        to80++;
        break;
    case "80 to 89":
        to90++;
        break;
    case "90 to 99":
        above90++;
        break;
    default:
        break;
}

但是，我得到了错误:

java: strings in switch are not supported in -source 1.6
  (use -source 7 or higher to enable strings in switch)

我知道一些答案将是:RTFE(即用错误替换手动).但我做到了.我尝试了以下方法: