private static int parsePercentage( String value )
		throws IllegalArgumentException, NumberFormatException
	{
		if( !value.endsWith( "%" ) )
			throw new NumberFormatException( "invalid percentage '" + value + "'" );

		int val;
		try {
			val = Integer.parseInt( value.substring( 0, value.length() - 1 ) );
		} catch( NumberFormatException ex ) {
			throw new NumberFormatException( "invalid percentage '" + value + "'" );
		}

		if( val < 0 || val > 100 )
			throw new IllegalArgumentException( "percentage out of range (0-100%) '" + value + "'" );
		return val;
	}
Syntax: [normal] [bold|+bold|-bold] [italic|+italic|-italic] [<size>|+<incr>|-<decr>|<percent>%] [family[, family]] [$baseFontKey]
flatlaf-core/src/main/java/com/formdev/flatlaf/UIDefaultsLoader.java