The problem with finding a laptop in this range is that the OS (Windows 7/8/8.1/10) automatically shaves away about 100 euros. In an ideal world where the OS isn't automatically bundled, you can get more/better hardware for your money. However, the world isn't fair and the option for the OS is wrested from you. I'm not saying that Windows is bad, but I am saying that it eats away at the hardware you'll get. There's literally no way to get a laptop in that range that can do light gaming that's new. You may end up having to go with either refurbished or used. If you choose to do this, this is your best bet at getting something that'll function for you.
Best recommendations:
{*} ASUS Laptop F554LA-WS52 Intel Core i5 5200U (2.20 GHz) 8 GB Memory 500 GB HDD Intel HD Graphics 5500 15.6" ~~ $400 USD (refurbished)
{*} ASUS Laptop F554LA-WS52 Intel Core i5 5200U (2.20 GHz) 8 GB Memory 500 GB HDD Intel HD Graphics 5500 15.6" ~~ $450 USD (new)
{*} ASUS Laptop F554LA-NH51 Intel Core i5 5200U (2.20 GHz) 4 GB Memory 500 GB HDD Intel HD Graphics 5500 15.6" ~~ $500 USD (new)
{*} ASUS Laptop D550MAV-DB01(S) Intel Celeron N2840 (2.16 GHz) 4 GB Memory 500 GB HDD Intel HD Graphics 15.6" ~~ $350 USD (new)
{*} ASUS Laptop K550LA-TS71T Intel Core i7 4500U (1.80GHz) 6GB Memory 750GB HDD Intel HD Graphics 4400 15.6" ~~ $490 USD (new)
{*} ASUS Laptop X Series X552LAV Intel Core i5 ~~ $390 USD (new)
I haven't recommended any other makers because I believe HPs, Lenovos, and Acers are literally worth less than used toilet paper (not recycled, literally already used). IBM and Dell make okay business-class laptops, but those are far beyond your budgetary reach.
When it comes to IDEs, the majority of those which target Java are very resource hungry. Eclipse, JetBrains IntelliJ IDEA, and even NetBeans can eat away at your CPU and RAM at the cost of rich and visual code completion and code example references. On the other hand, something like Vim (which is what I use) is very spartan and minimalistic and, while it has code completion options available, it's not as friendly for people starting out in programming (but, the benefit is that it forces you to literally memorize standard libraries, frameworks, and APIs).