QuotedString.java

/**
 * \file  QuotedString.java
 * \brief EO sample
 */


/**
 * Notice the benefits I gained:
 *
 * - The object is lazy — it doesn’t perform any calculations if not needed.
 * - It is easy to test.
 * - It is small, so it is easy to maintain in the future.
 * - It is easy to use in collections. You can wrap multiple items in a collection with the object,
 *    but in the end use just a few of them. This way you will not perform heavy calculations
 *    on the entire collection if not needed.
 * - It is immutable.
 * - It is cheap to create. Java is designed to create new objects.
 */

/**
 * Put quotes around the given String if necessary.
 * <p>
 * If the argument doesn't include spaces or quotes, return it as is. If it
 * contains double quotes, use single quotes - else surround the argument by
 * double quotes.
 * </p>
 * <p>
 * Copied from Apache Commons Exec: http://commons.apache.org/proper/commons-exec/
 */

class QuotedString
{
    private static final String SINGLE_QUOTE = "\'";
    private static final String DOUBLE_QUOTE = "\"";

    private final String argument;

    public QuotedString(String argument)
	{
        this.argument = argument;
    }

    public String toString()
	{
        String cleanedArgument = argument.trim();

        // strip the quotes from both ends
        while (cleanedArgument.startsWith(SINGLE_QUOTE) ||
               cleanedArgument.startsWith(DOUBLE_QUOTE))
        {
            cleanedArgument = cleanedArgument.substring(1);
        }

        while (cleanedArgument.endsWith(SINGLE_QUOTE) ||
               cleanedArgument.endsWith(DOUBLE_QUOTE))
        {
            cleanedArgument = cleanedArgument.substring(0, cleanedArgument.length() - 1);
        }

        final StringBuilder buf = new StringBuilder();

        if (cleanedArgument.contains(DOUBLE_QUOTE)) {
            if (cleanedArgument.contains(SINGLE_QUOTE)) {
                throw new IllegalArgumentException("Can't handle single and double quotes in same argument");
            }

            return buf
                .append(SINGLE_QUOTE)
                .append(cleanedArgument)
                .append(SINGLE_QUOTE)
                .toString();
        }
		else if (cleanedArgument.contains(SINGLE_QUOTE) ||
                 cleanedArgument.contains(" "))
        {
            return buf
                .append(DOUBLE_QUOTE)
                .append(cleanedArgument)
                .append(DOUBLE_QUOTE)
                .toString();
        }
		else {
            return cleanedArgument;
        }
    }
}
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