EC
IllegalArgumentException
JavaERRORCommonValidation

Illegal or inappropriate method argument

Quick Answer

Validate arguments at method entry and throw IllegalArgumentException with a descriptive message.

What this means

Thrown to indicate that a method has been passed an illegal or inappropriate argument. Use it in your own APIs to enforce preconditions.

Why it happens
  1. 1Negative value passed where positive required
  2. 2Null passed to a method requiring non-null

Fix

Precondition check at method entry

Precondition check at method entry
void setAge(int age) {
    if (age < 0 || age > 150)
        throw new IllegalArgumentException("Invalid age: " + age);
    this.age = age;
}

Why this works

Failing fast at the entry point makes the bug site obvious in stack traces.

Code examples
Triggerjava
Thread.sleep(-1); // IllegalArgumentException
Custom validationjava
if (timeout <= 0)
    throw new IllegalArgumentException("timeout > 0 required, got: " + timeout);
Guava Preconditionsjava
Preconditions.checkArgument(n > 0, "n must be positive: %s", n);
Sources
Official documentation ↗

Java SE Documentation

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