IntelliJ IDEA vs WinMerge

IDEA places an emphasis in safe refactoring, offering a variety of features to make this possible for a variety of languages.
These features include safe delete, type migration and replacing method code duplicates.

Uses a fast indexing technique to provide contextual hints (auto-completion, available object members, import suggestions).
On-the-fly code analysis to detect errors and propose refactorization.

A very complete development environment support.

IntelliJ supports many languages besides Java, some of these are: golang, Scala, Clojure, Groovy, Bash, etc.

Many plugins are available for almost any task a developer may need to cover. Plugins are developed by Jetbrains themselves or by 3rd parties through the SDK available for writing them.

IntelliJ IDEA hardly ever crashes or has any issues that plague other Java IDEs like file corruption or slowness.

IDEA has a clean, intuitive interface with some customization available (such as the Darcula theme).

The documentation is exhaustive, easy to navigate, and clearly worded.

With ability to step into a certain part of a large method invocation (Shift+F7), drop frame, executing code snippets, showing method return values, etc.

There is a free community edition (open source) and an ultimate edition, which you can compare here.

The ultimate edition is available for free for one year for students but must be registered through an .edu e-mail account.

These simplify the daily work, e.g. copy/cut a whole line without the need to select it.

Verify yourselves as a student to get more perks.

Creating an embedded database, running SQL script in a dedicated terminal, viewing tables and their contents, and creating a connection to an in-memory or embedded database is fully supported.

I pay $24 a month and i have access to all jetbrain peoducts , so i use their many tools , i tried many others like netbeans , eclipse , etc , they re good but intelij is on the space and the sky is the limit . Been using it for 5 years and i cant tell i got frustrated using .it

You can quickly copy changed lines (or files in folder comparison) in both directions with keyboard shortcuts. You can edit the files as well, with syntax highlighting of some languages.

Can show what files has been changed in a folder, allows comparing files in tabs.

Can show differences within a line.

Winmerge is a free and open source tool.

Select two files and compare them. Alternatively, select one file, navigate elsewhere, select the other file to compare.
Also supports drag'n'drop of files / folders from Explorer.
History of past comparisons.

Binary is less than 3 MB, so it starts quickly

Can filter out files for folder comparison, lines for file comparisons, with regular expressions.
Options also allow to ignore whitespace differences, white lines, case change, line-ending changes, etc.

Keyboard shortcuts (and toolbar buttons) to navigate to next (previous) difference, side panel shows a map of the files with changed lines and allows to jump to a given place.

Detects when a block of lines has been moved in the file and shows the relation.