IntelliJ IDEA is a very good Java IDE. Most of its commands have shortcuts to keep your hands from leaving the keyboard.
Ctrl Space — Basic code completion
Ctrl Shift Space — Smart code completion
Ctrl Shift Enter — Complete statement
Ctrl P — Parameter info
Ctrl Q — Quick documentation lookup
Shift F1 — External Doc
Ctrl hover — Brief Info
Ctrl F1 — Error or warning at caret
Alt Insert — Generate code
Ctrl O — Override methods
Ctrl I — Implement methods
Ctrl Alt T — Surround with
Ctrl / — Comment or uncomment line
Ctrl Shift / — Comment or uncomment block
Ctrl W — Select successively increasing code blocks
Ctrl Shift W — Decrease current selection to previous state
Alt Q — Context info
Alt Enter — Show intention actions and quick-fixes
Ctrl Alt L — Reformat code
Ctrl Alt O — Optimize imports
Ctrl Alt I — Auto-indent line(s)
Tab — Indent selected lines
Shift Tab — Unindent selected lines
Ctrl X — Cut current line or selected block to clipboard
Ctrl C — Copy current line or selected block to clipboard
Ctrl V — Paste from clipboard
Ctrl Shift V — Paste from recent buffers
Ctrl D — Duplicate current line or selected block
Ctrl Y — Delete line at caret
Ctrl Shift J — Smart line join
Ctrl Enter — Smart line split
Shift Enter — Start new line
Ctrl Shift U — Toggle case for word at caret or selected block
Ctrl Shift ] / [ — Select till code block end/start
Ctrl Backspace — Delete to word end/start
Ctrl + / - — Expand/collapse code block
Ctrl Shift + — Expand all
Ctrl Shift - — Collapse all
Ctrl F4 — Close active editor tab
Alt F7 / Ctrl F7 — Find usages/Find usages in file
Ctrl Shift F7 — Highlight usages in file
Ctrl Alt F7 — Show usages
Ctrl N — Go to class
Ctrl Shift N — Go to file
Ctrl Alt Shift N — Go to symbol
Alt Right / Left — Go to next / previous editor tab
F12 — Go back to previous tool window
Esc — Go to editor
Shift Esc — Hide active or last active window
Ctrl Shift F4 — Close active run, messages...
Ctrl G — Go to line
Ctrl E — Recent files popup
Ctrl Alt Left / Right — Navigate back / forward
Ctrl Shift Backspace — Navigate to last edit location
Alt F1 — Select current file or symbol in any view
Ctrl B / Ctrl Click — Go to declaration
Ctrl Alt B — Go to implementation(s)
Ctrl Shift I — Open quick definition lookup
Ctrl Shift B — Go to type declaration
Ctrl U — Go to super-method / super-class
Alt Up / Down — Go to previous / next method
Ctrl ]/[ — Move to code block end/start
Ctrl F12 — File structure popup
Ctrl H — Type hierarchy
Ctrl Shift H — Method hierarchy
Ctrl Alt H — Call hierarchy
F2 / Shift F2 — Next/previous highlighted error
F4 / Ctrl Enter — Edit source / View source
Alt Home — Show navigation bar
F11 — Toggle bookmark
Ctrl F11 — Toggle bookmark with mnemonic
Ctrl 0...9 — Go to numbered bookmark
Shift F11 — Show bookmarks
Double Shift — Search everywhere
Ctrl F — Find
F3 Shift F3 — Find next / Find previous
Ctrl R — Replace
Ctrl Shift F — Find in path
Ctrl Shift R — Replace in path
Ctrl Alt J — Surround with Live Template
Ctrl J — Insert Live Template
iter — Iteration according to Java SDK 1.5 style
inst — Check object type with instanceof and downcast it
itco — Iterate elements of java.util.Collection
itit — Iterate elements of java.util.Iterator
itli — Iterate elements of java.util.List
psf — public static final
thr — throw new
F5 — Copy
F6 — Move
Alt Delete — Safe Delete
Shift F6 — Rename
Ctrl F6 — Change Signature
Ctrl Alt N — Inline
Ctrl Alt M — Extract Method
Ctrl Alt V — Extract Variable
Ctrl Alt F — Extract Field
Ctrl Alt C — Extract Constant
Ctrl Alt P — Extract Parameter
F8/F7 — Step over/Step into
Shift F7 / Shift F8 — Smart step into/Step out
Alt F9 — Run to cursor
Alt F8 — Evaluate expression
F9 — Resume program
Ctrl F8 — Toggle breakpoint
Ctrl Shift F8 — View breakpoints
Ctrl F9 — Make project
Ctrl Shift F9 — Compile selected file, package or module
Alt Shift F10 / F9 — Select configuration and run/and debug
Shift F10 / F9 — Run/Debug
Ctrl Shift F10 — Run context configuration from editor
Ctrl K — Commit project to VCS
Ctrl T — Update from VCS
Alt Shift C — View recent changes
Alt ` — VCS Operations Popup
Alt 0...9 — Open corresponding tool window
Ctrl S — Save all
Ctrl Alt Y — Synchronize
Ctrl Shift F12 — Toggle maximizing editor
Alt Shift F — Add to Favorites
Alt Shift I — Inspect current file
Ctrl ` — Quick switch current scheme
Ctrl Alt S — Open Settings dialog
Ctrl Alt Shift S — Open Project Structure dialog
Ctrl Shift A — Find Action
Ctrl Tab — Switch between tool and tabs