Hi Tony Jin welcome to Javaranch As said by Paul, the problem is with the "I" actually is small letter "l" (as in look). And Java is case sensitive.
The errors comes out pointing at the dot saying "cannot find symbol". Is something wrong with my keyboard or something?
The error is shown at the .(dot) because the compiler can resolve the System and the out object but cannot resolve the "printIn" method since there is no such method. When you see errors like those, first thing to check is typing mistakes, then syntax errors and finally if the variable or method pointed by the error message is really available at that point.