Java : IllegalArgumentException with Examples

IllegalArgumentException (Java SE 21 & JDK 21) with Examples.
You will find code examples on most IllegalArgumentException methods.

Summary

Thrown to indicate that a method has been passed an illegal or inappropriate argument.

Class diagram

public void func(String str) {
    if (str == null) {
        throw new IllegalArgumentException("str is null!");
    }
    if (str.isEmpty()) {
        throw new IllegalArgumentException("str is empty!");
    }

    System.out.println(str);
}

func("abcd"); // abcd

func(null); // java.lang.IllegalArgumentException: str is null!

func(""); // java.lang.IllegalArgumentException: str is empty!

If you only check for null or not, it is recommended to use the Objects.requireNonNull method instead.

public void func(String str) {
    Objects.requireNonNull(str, "str is null!");

    System.out.println(str);
}

func("abcd"); // abcd

func(null); // java.lang.NullPointerException: str is null!

Constructors

IllegalArgumentException ()

Constructs an IllegalArgumentException with no detail message.

final var e = new IllegalArgumentException();
System.out.println(e); // java.lang.IllegalArgumentException

IllegalArgumentException (String s)

Constructs an IllegalArgumentException with the specified detail message.

final var e = new IllegalArgumentException("abcde");
System.out.println(e); // java.lang.IllegalArgumentException: abcde
System.out.println(e.getMessage()); // abcde

IllegalArgumentException (String message, Throwable cause)

Constructs a new exception with the specified detail message and cause.

final var cause = new IllegalArgumentException("XYZ");
final var e = new IllegalArgumentException("abcde", cause);

System.out.println(e); // java.lang.IllegalArgumentException: abcde
System.out.println(e.getMessage()); // abcde

System.out.println(e.getCause()); // java.lang.IllegalArgumentException: XYZ
System.out.println(e.getCause().getMessage()); // XYZ

IllegalArgumentException (Throwable cause)

Constructs a new exception with the specified cause and a detail message of (cause==null ? null : cause.toString()) (which typically contains the class and detail message of cause).

final var cause = new IllegalArgumentException("XYZ");
final var e = new IllegalArgumentException(cause);

System.out.println(e); // java.lang.IllegalArgumentException: java.lang.IllegalArgumentException: XYZ
System.out.println(e.getMessage()); // java.lang.IllegalArgumentException: XYZ

System.out.println(e.getCause()); // java.lang.IllegalArgumentException: XYZ
System.out.println(e.getCause().getMessage()); // XYZ

Methods declared in Throwable

addSuppressed, fillInStackTrace, getCause, getLocalizedMessage, getMessage, getStackTrace, getSuppressed, initCause, printStackTrace, printStackTrace, printStackTrace, setStackTrace, toString

Please see the link below.

Throwable with Examples

API Examples