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java · brace indent · live · client-side

Format Java source files

A brace-tracking indenter for Java. Re-indents classes, methods, and lambda bodies. Use google-java-format for production. Runs locally.

Java Formatter
Input
85 B
1 lines
Output
86 B
2 lines
Status
ready
live
Ratio
1.01×
out/in
input · java
output · formatted java
public class Hello{public static void main(String[] args){System.out.println("Hi");}}
Quick Start

How to format Java

Tracks brace depth across class, method, and lambda bodies — re-pads each line to match.

  1. 01

    Paste Java source

    Classes, records, enums, and lambdas all flow through.

    Parsing runs through Prettier’s standalone bundle (or the language-specific equivalent) loaded lazily — no parser ships until the tool is opened.

    javaPrettierASTstandalonelazy
    input · sourceraw · AST
    class A{}
    loaded · parsedAST · ready
  2. 02

    Pick indent width

    4 spaces is Oracle's default; 2 is the Google style.

    Indent width, tab style, and print-width re-format through a memoised pass — switching 2 → 4 spaces never re-parses, only re-prints.

    optionsindentprint-widthmemoisedlive
    opts · optionsindent · live
    indent=4
    options applied · livelive
  3. 03

    Watch blocks align

    Class, method, and try-with-resources bodies all indent based on brace depth.

    The formatter is deterministic and idempotent: running it twice produces byte-identical output, which keeps diffs and git noise to a minimum.

    liveidempotentdeterministicdiff-cleanstable
    out · formattedindented · ready
    class A {
    void m() {}
}
    formatted · liveidempotent
  4. 04

    Copy or download

    Export as .java or copy. Source stays in your browser.

    Download writes a Blob with the language-appropriate extension; copy uses navigator.clipboard.writeText so the output preserves all whitespace exactly.

    exportclipboardbloblanguage MIMEclient-side
    ok · copiedready · done
    ✓ Copied
    shipped · ready to shipsuccess
Pro tips

Formatting tips that keep diffs sane

Pick one config and pin it

Inconsistent formatting causes diff churn. Commit .prettierrc / .editorconfig and enforce in CI.

Format on save

Editor integration is faster feedback than a pre-commit hook. Use both for belt-and-braces.

Idempotency matters

Running the formatter twice should produce identical output. Test this on a representative file.

Match the language community

Default to community conventions: 2 spaces for JS/CSS, 4 for Python, tabs for Go. Fights over indent are a productivity tax.

Print-width drives wrapping

80, 100, and 120 are the common targets. Wider lines parse fast but review slower side-by-side.

Don’t mix formatters and linters

Prettier handles whitespace; ESLint handles correctness. Disable overlapping rules to avoid fight-club configs.

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Use Cases

When to format Java

Codegen, gist cleanup, learning Java.

Codegen output

Re-indent code emitted by annotation processors or stub generators. Idempotent: running the formatter twice produces byte-identical output, which is the foundation of a clean CI gate. Pair with a pre-commit hook so PRs arrive already formatted, focusing review on logic.

idempotent

Gist cleanup

Tidy samples pasted from blogs and Stack Overflow. Pairs with EditorConfig + .prettierrc for end-to-end consistency. Whitespace-only changes vanish so reviewers see real diffs, and git blame stays honest about who wrote what.

CI-ready

Tutorial code

Make compressed textbook examples readable. Output respects your indent width, tab style, and print-width — settings carry over for repeat runs. Switching 2-space to 4-space costs nothing in CPU but standardises an entire codebase.

diff-clean

Code review

Strip whitespace churn so diffs show real changes. Format-on-save is the fastest feedback loop; CI is the safety net. Together they make inconsistent indentation a thing of the past and free up review cycles for genuine concerns.

PR-friendly

Quick fix

Reformat without opening IntelliJ or Eclipse. Whitespace-only changes don't trigger downstream content-hash invalidations, so CDN cache keys and CI cache layers stay warm. Real changes get all the rebuild budget.

review-ready

Docs examples

Standardise Java examples in technical docs. Pairs with linters (ESLint, Stylelint, pylint) that catch what formatting alone can't — bugs, unused imports, dead code. Each tool stays in its lane, and the codebase stays clean.

deterministic
FAQ

Frequently asked questions

No — it's a brace-tracking indenter. Run google-java-format for canonical Google style.
Angle brackets are not counted as braces; only { } [ ] ( ) affect indent depth.
Their bodies indent based on brace depth like any class.
Annotations stay on their original lines; only indentation changes.
No — the formatter runs locally in your browser tab.
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