三大神器：

官方网址: http://www.jetbrains.com/idea/

官方网址: https://code.visualstudio.com/

官方网址: http://www.eclipse.org

装好了idea社区版，并试运行以下代码，OK！

//TIP To <b>Run</b> code, press <shortcut actionId="Run"/> or
// click the <icon src="AllIcons.Actions.Execute"/> icon in the gutter.
public class Main {public static void main(String[] args) {//TIP Press <shortcut actionId="ShowIntentionActions"/> with your caret at the highlighted text// to see how IntelliJ IDEA suggests fixing it.System.out.printf("Hello and welcome!");for (int i = 1; i <= 5; i++) {//TIP Press <shortcut actionId="Debug"/> to start debugging your code. We have set one <icon src="AllIcons.Debugger.Db_set_breakpoint"/> breakpoint// for you, but you can always add more by pressing <shortcut actionId="ToggleLineBreakpoint"/>.System.out.println("i = " + i);}}
}