jaffirm

jaffirm

The jaffirm package provides simple and fast pre/postcondition and invariant checking functions.

Features

• Static invocation, zero-allocation code paths for the common case of non-failing contracts.
• Specialized and generic variants of all functions for use in low-latency software.
• Detailed contract failure messages by construction.
• Written in pure Java 17.
• High coverage test suite.
• OSGi-ready
• JPMS-ready
• ISC license.

Usage

Declare preconditions with the Preconditions class. Declare postconditions with the Postconditions class. Declare invariants with the Invariants class.

import static com.io7m.jaffirm.core.Contracts.conditionI;
import static com.io7m.jaffirm.core.Preconditions.checkPreconditionI;
import static com.io7m.jaffirm.core.Preconditions.checkPreconditionsI;

int exampleSingles(final int x)
{
  checkPreconditionI(x, x > 0,      i -> "Input " + i + " must be > 0");
  checkPreconditionI(x, x % 2 == 0, i -> "Input " + i + " must be even");
  return x * 2;
}

int exampleMultis(final int x)
{
  checkPreconditionsI(
    x,
    conditionI(i -> i > 0,      i -> "Input " + i + " must be > 0"),
    conditionI(i -> i % 2 == 0, i -> "Input " + i + " must be even"));
  return x * 2;
}

> exampleSingles(0)
Exception in thread "main" com.io7m.jaffirm.core.PreconditionViolationException: Precondition violation.
  Received: 0
  Violated conditions:
    [0]: Input 0 must be > 0

> exampleSingles(1)
Exception in thread "main" com.io7m.jaffirm.core.PreconditionViolationException: Precondition violation.
  Received: 1
  Violated conditions:
    [0]: Input 1 must be even

> exampleMultis(-1)
Exception in thread "main" com.io7m.jaffirm.core.PreconditionViolationException: Precondition violation.
  Received: -1
  Violated conditions:
    [0]: Input -1 must be > 0
    [1]: Input -1 must be even