juneau-core/juneau-marshall/src/main/java/org/apache/juneau/uon/UonUtils.java

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package org.apache.juneau.uon;

import static org.apache.juneau.internal.StringUtils.*;

import org.apache.juneau.internal.*;

/**
 * Utility methods for the UON and UrlEncoding serializers and parsers.
 */
public final class UonUtils {

	private static final AsciiSet needsQuoteChars = AsciiSet.create("),=\n\t\r\b\f ");
	private static final AsciiSet maybeNeedsQuotesFirstChar = AsciiSet.create("),=\n\t\r\b\f tfn+-.#0123456789");

	/**
	 * Returns <jk>true</jk> if the specified string needs to be quoted per UON notation.
	 *
	 * <p>
	 * For example, strings that start with '(' or '@' or look like boolean or numeric values need to be quoted.
	 *
	 * @param s The string to test.
	 * @return <jk>true</jk> if the specified string needs to be quoted per UON notation.
	 */
	public static final boolean needsQuotes(String s) {
		char c0 = s.isEmpty() ? 0 : s.charAt(0);
		return (
			s.isEmpty()
			|| c0 == '@'
			|| c0 == '('
			|| needsQuoteChars.contains(s)
			|| (
				maybeNeedsQuotesFirstChar.contains(c0)
				&& (
					"true".equals(s)
					|| "false".equals(s)
					|| "null".equals(s)
					|| isNumeric(s)
				)
			)
		);
	}
}