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package org.graalvm.options;

import java.util.Collections;
import java.util.Map;
import java.util.Set;

Represents a mapping between String keys and values. Allows to create 
options to group/accumulate key=value pairs, with a common prefix; whose keys are not known beforehand e.g. user defined properties. 
Type parameters:
<T> – the class of the map values
Since:
19.2/**
 * Represents a mapping between {@link String} keys and values. Allows to create {@link OptionKey
 * options} to group/accumulate {@code key=value} pairs, with a common prefix; whose keys are not
 * known beforehand e.g. user defined properties.
 *
 * @param <T> the class of the map values
 *
 * @since 19.2
 */
public final class OptionMap<T> {

    private static final OptionMap<?> EMPTY = new OptionMap<>(Collections.emptyMap());

    final Map<String, T> backingMap;
    final Map<String, T> readonlyMap;

    OptionMap(Map<String, T> map) {
        this.backingMap = map;
        this.readonlyMap = Collections.unmodifiableMap(map);
    }

    
Returns an empty option map (immutable).
Type parameters:
<T> – the class of the map values
Returns:
an empty option map
Since:
19.2/**
     * Returns an empty option map (immutable).
     * 
     * @param <T> the class of the map values
     * @return an empty option map
     * @since 19.2
     */
    @SuppressWarnings("unchecked")
    public static <T> OptionMap<T> empty() {
        return (OptionMap<T>) EMPTY;
    }

    
Returns the value to which the specified key is mapped, or null if this option map contains no mapping for the key. 
Params:
key – the key whose associated value is to be returned
Returns:
the value to which the specified key is mapped, or null if this map contains no mapping for the key
Since:
19.2/**
     * Returns the value to which the specified key is mapped, or {@code null} if this option map
     * contains no mapping for the key.
     *
     * @param key the key whose associated value is to be returned
     * @return the value to which the specified key is mapped, or {@code null} if this map contains
     *         no mapping for the key
     *
     * @since 19.2
     */
    public T get(String key) {
        return readonlyMap.get(key);
    }

    
Returns an unmodifiable Set view of the mappings contained in this map. 
Returns:
a set view of the mappings contained in this map
Since:
19.2/**
     * Returns an unmodifiable {@link Set} view of the mappings contained in this map.
     *
     * @return a set view of the mappings contained in this map
     *
     * @since 19.2
     */
    public Set<Map.Entry<String, T>> entrySet() {
        return readonlyMap.entrySet();
    }

    
Since:
19.2/**
     * @since 19.2
     */
    @Override
    public int hashCode() {
        return readonlyMap.hashCode();
    }

    
Since:
19.2/**
     * @since 19.2
     */
    @SuppressWarnings("unchecked")
    @Override
    public boolean equals(Object obj) {
        if (obj instanceof OptionMap) {
            return readonlyMap.equals(((OptionMap<T>) obj).readonlyMap);
        }
        return false;
    }
}