65 lines
1.5 KiB
Java
65 lines
1.5 KiB
Java
package envoy.event;
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import java.io.Serializable;
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import java.util.Objects;
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/**
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* This class serves as a convenience base class for all events. It provides a generic value. For
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* events without a value there also is {@link envoy.event.Event.Valueless}.
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*
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* @author Kai S. K. Engelbart
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* @param <T> the type of the Event
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* @since Envoy v0.2-alpha
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*/
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public abstract class Event<T> implements Serializable {
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protected final T value;
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private static final long serialVersionUID = 0L;
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protected Event(T value) {
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this(value, false);
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}
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/**
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* This constructor is reserved for {@link Valueless} events. No other event should contain null
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* values. Only use if really necessary. Using this constructor with {@code true} implies that
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* the user has to manually check if the value of the event is null.
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*/
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protected Event(T value, boolean canBeNull) {
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this.value = canBeNull ? value : Objects.requireNonNull(value);
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}
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/**
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* @return the data associated with this event
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*/
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public T get() {
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return value;
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}
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@Override
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public String toString() {
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return String.format("%s[value=%s]", this.getClass().getSimpleName(), value);
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}
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/**
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* Serves as a super class for events that do not carry a value.
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*
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* @author Kai S. K. Engelbart
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* @since Envoy Common v0.2-alpha
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*/
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public static abstract class Valueless extends Event<Void> {
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private static final long serialVersionUID = 0L;
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protected Valueless() {
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super(null, true);
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}
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@Override
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public String toString() {
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return this.getClass().getSimpleName();
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}
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}
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}
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