I am interested to do practice on oracle database.Actually i had completed course on MYSQL,now i want to try on oracle.Today i have opened the oracle website to download oracle 11g(windows7 64bit),But in downloads only Oracle Database 11g Express Edition R2 is there.What to do now?For Mysql workbench is there then what about oracle is there any IDE?

Am sure Oracle has developer tools. Did you check their website?

Oracle 12c is the current production release.
11g is still in widespread use.
10g is being phased out by most customers, though there's still a lot of legacy installations out there.
9i and earlier, forget about it. There's no money in it from the very few way outdated installations out there that for whatever reason have never been upgraded.

And yes, Oracle has its tools available on their website. SQLDeveloper is what you're looking for.
Many professional DBAs and DBDs however use 3rd party tools like TOAD and SQLDeveloper, which are very nice but pretty expensive.