UnmodifiableMapCollector.java
package net.morimekta.collect.collectors;
import net.morimekta.collect.UnmodifiableMap;
import net.morimekta.collect.UnmodifiableSet;
import java.util.Set;
import java.util.function.BiConsumer;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collector;
public class UnmodifiableMapCollector<E, K, V> implements Collector<E, UnmodifiableMap.Builder<K, V>, UnmodifiableMap<K, V>> {
private final Function<E, K> toKey;
private final Function<E, V> toValue;
public UnmodifiableMapCollector(Function<E, K> toKey, Function<E, V> toValue) {
this.toKey = toKey;
this.toValue = toValue;
}
@Override
public Supplier<UnmodifiableMap.Builder<K, V>> supplier() {
return UnmodifiableMap::newBuilder;
}
@Override
public BiConsumer<UnmodifiableMap.Builder<K, V>, E> accumulator() {
return (b, e) -> b.put(toKey.apply(e), toValue.apply(e));
}
@Override
public BinaryOperator<UnmodifiableMap.Builder<K, V>> combiner() {
return (b1, b2) -> b1.putAll(b2.build());
}
@Override
public Function<UnmodifiableMap.Builder<K, V>, UnmodifiableMap<K, V>> finisher() {
return UnmodifiableMap.Builder::build;
}
@Override
public Set<Characteristics> characteristics() {
return UnmodifiableSet.setOf();
}
}