Example usage for java.util Collections emptyMap

Introduction

In this page you can find the example usage for java.util Collections emptyMap.

Prototype

@SuppressWarnings("unchecked")
public static final <K, V> Map<K, V> emptyMap()

Source Link

Document

Returns an empty map (immutable).

Usage

From source file:Main.java

public static <K, V> Map<K, V> copyNullSafeHashMapWithNullValues(Map<? extends K, ? extends V> map) {
    if (map.isEmpty()) {
        return Collections.emptyMap();
    }/*w  w  w.j av  a2s . c om*/
    return Collections.unmodifiableMap(copyNullSafeMutableHashMapWithNullValues(map));
}

From source file:Main.java

/**
 * Returns an non null value based on the giving {@link Map}
 *
 * @param map/*w ww  . j  a v a  2 s. c  o m*/
 *            value to evaluate
 * @return the original value or an empty {@link Map}
 * @since 4.2
 */
public static <K, V> Map<K, V> nonNullMap(@Nullable final Map<K, V> map) {
    return map == null ? Collections.emptyMap() : map;
}

From source file:Main.java

/**
 * Parses and returns CGI arguments./*from  w  ww  .j  av  a 2s  . co  m*/
 * 
 * @param rest the string to parse
 * @return CGI arguments from <tt>rest</tt>
 */
public static Map<String, String> parseArgs(final String rest) {
    if (isEmpty(rest))
        return Collections.emptyMap();
    final Map<String, String> res = new HashMap<String, String>(3);
    for (StringTokenizer st = new StringTokenizer(rest, "&", false); st.hasMoreTokens();) {
        final String pair = st.nextToken();
        final int ieq = pair.indexOf('=');
        String key, val;
        if (ieq == -1) {
            key = pair;
            val = null;
        } else {
            key = pair.substring(0, ieq);
            val = pair.substring(ieq + 1);
        }
        res.put(key.trim(), val == null ? val : val.trim());
    }
    return res;
}

From source file:Main.java

public static Map<String, Object> fromJson(String params) {
    try {/* ww  w .  j ava 2s .c  o m*/
        JavaType jType = getCollectionType(Map.class, String.class, Object.class);
        return mapper.readValue(params, jType);
    } catch (Exception e) {
        return Collections.emptyMap();
    }
}

From source file:Main.java

/** */
public static Map<QName, String> toQName(Map<String, String> setProps) {
    if (setProps == null) {
        return Collections.emptyMap();
    }//www  .  j ava 2  s .  co m
    Map<QName, String> result = new HashMap<QName, String>(setProps.size());
    for (Map.Entry<String, String> entry : setProps.entrySet()) {
        result.put(createQNameWithCustomNamespace(entry.getKey()), entry.getValue());
    }
    return result;
}

From source file:Maps.java

public static <K, V> Map<K, V> create() {
    return Collections.emptyMap();
}

From source file:Main.java

/**
 * Wraps a possibly null map in an immutable wrapper.
 *
 * @param <K> the key type/*from  ww w .  j ava  2s. c  o  m*/
 * @param <V> the value type
 * @param source Nullable map to wrap.
 * @return {@link Collections#unmodifiableMap(java.util.Map)} if given map is not null, otherwise
 * {@link java.util.Collections#emptyMap()}.
 */
public static <K, V> Map<K, V> wrap(final Map<K, V> source) {
    if (source != null) {
        return new HashMap<>(source);
    }
    return Collections.emptyMap();
}

From source file:Main.java

/**
 * Combines two lists into map, using first list as keys and second as values
 *
 * @param keys   List used as keys//from w ww .ja  v  a 2  s.  c  o m
 * @param values List used as values
 * @param <K>    Type of values in keys list
 * @param <V>    Type of values in values list
 * @return {@link LinkedHashMap}
 */
public static <K, V> Map<K, V> combineLists(List<? extends K> keys, List<? extends V> values) {
    if (keys.size() != values.size()) {
        throw new IllegalArgumentException("Cannot combine lists with dissimilar sizes");
    }

    if (keys.isEmpty() && values.isEmpty()) {
        return Collections.emptyMap();
    }

    int size = values.size();

    Map<K, V> map = new LinkedHashMap<>(size);
    for (int i = 0; i < size; i++) {
        map.put(keys.get(i), values.get(i));
    }

    return map;
}

From source file:Main.java

@SuppressWarnings({ "rawtypes", "unchecked" })
public static <K, V> Map newMap(Object... keysAndValues) {
    if (keysAndValues == null) {
        return Collections.emptyMap();
    }//from  ww w .jav  a  2  s  .  c o m
    if (keysAndValues.length % 2 == 1) {
        throw new IllegalArgumentException("Must have an even number of keys and values");
    }

    Map<K, V> map = new HashMap<K, V>();
    for (int i = 0; i < keysAndValues.length; i += 2) {
        map.put((K) keysAndValues[i], (V) keysAndValues[i + 1]);
    }
    return map;
}

From source file:Main.java

@SuppressWarnings({ "rawtypes", "unchecked" })
public static <K, V> Map newMap(Object... keysAndValues) {
    if (keysAndValues == null) {
        return Collections.emptyMap();
    }/*from w  w w.j  a v a 2 s  .co m*/
    if (keysAndValues.length % 2 == 1) {
        throw new IllegalArgumentException("Must have an even number of keys and values");
    }

    Map<K, V> map = new HashMap<>();
    for (int i = 0; i < keysAndValues.length; i += 2) {
        map.put((K) keysAndValues[i], (V) keysAndValues[i + 1]);
    }
    return map;
}