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edn-java is an parser and printer for 'edn' written in Java, for Java and requiring no external dependencies.

There is a newer version: 0.7.1

// (c) 2012 B Smith-Mannschott -- Distributed under the Eclipse Public License
package us.bpsm.edn;

import static us.bpsm.edn.Symbol.newSymbol;

/**
 * A Keyword is {@linkplain Named}. Additionally it obeys the syntactic
 * restrictions defined for edn Keywords.
 * 
 * Note: Keywords print with a leading colon, but this is not part of the
 * keyword's name:
 * 
 * 
 * {@code // For the keyword ":foo/bar"
 * Keyword k = newKeyword("foo", "bar");
 * k.getName()   => "bar"
 * k.getPrefix() => "foo"
 * k.toString()  => ":foo/bar"}
 * 
 */
public final class Keyword implements Named, Comparable {
    private final Symbol sym;

    /** {@inheritDoc} */
    public final String getPrefix() {
        return sym.getPrefix();
    }

    /** {@inheritDoc} */
    public final String getName() {
        return sym.getName();
    }

    public static Keyword newKeyword(Symbol sym) {
        return INTERNER.intern(sym, new Keyword(sym));
    }

    /**
     * Provide a Keyword with the given prefix and name.
     * 
     * Keywords are interned, which means that any two keywords which are equal
     * (by value) will also be identical (by reference).
     * 
     * @param prefix
     *            An empty String or a non-empty String obeying the restrictions
     *            specified by edn. Never null.
     * @param name
     *            A non-empty string obeying the restrictions specified by edn.
     *            Never null.
     * @return a Keyword, never null.
     */
    public static Keyword newKeyword(String prefix, String name) {
        return newKeyword(newSymbol(prefix, name));
    }

    /**
     * This is equivalent to {@code newKeyword("", name)}.
     * 
     * @param name
     *            A non-empty string obeying the restrictions specified by edn.
     *            Never null.
     * @return a Keyword without a prefix, never null.
     * @see #newKeyword(String, String)
     */
    public static Keyword newKeyword(String name) {
        return newKeyword(newSymbol(EMPTY, name));
    }

    /**
     * Return a Keyword with the same prefix and name as {@code sym}.
     * @param sym a Symbol, never null
     * @return a Keyword with the same prefix and name as {@code sym}.
     */
    private Keyword(Symbol sym) {
        if (sym == null) {
            throw new NullPointerException();
        }
        this.sym = sym;
    }

    public String toString() {
        return ":" + sym.toString();
    }

    public int compareTo(Keyword o) {
        if (this == o) {
            return 0;
        }
        return sym.compareTo(o.sym);
    }

    private static final Interner INTERNER = new Interner();

}