Summary

Adding an isEmpty default method to CharSequence would harmonize String with other CharSequence implementations (StringBuilder etc).

Problem

isEmpty is shorter and more concise than length() == 0. Checking for and filtering out empty Strings and other CharSequences is a common occurrence in code, and having an explicit method allows its use as a method reference.

Solution

Add a default method isEmpty() to CharSequence.

Specification

Add the following to java.lang.CharSequence:

/**
 * Returns {@code true} if this character sequence is empty.
 *
 * @implSpec
 * The default implementation returns the result of calling {@code length() == 0}.
 *
 * @return {@code true} if {@link #length()} is {@code 0}, otherwise
 * {@code false}
 *
 * @since 15
 */
default boolean isEmpty() {
    return this.length() == 0;
}

Also add an override with clarifications to java.nio.CharBuffer:

/**
 * Returns {@code true} if this character buffer is empty.
 *
 * @return {@code true} if there are {@code 0} remaining characters,
 *         otherwise {@code false}
 *
 * @since 15
 */
public final boolean isEmpty() {
    return remaining() == 0;
}