src/game/java/net/minecraft/world/Nameable.java

package net.minecraft.world;

import javax.annotation.Nullable;
import net.minecraft.network.chat.Component;

public interface Nameable {
    Component getName();

    default boolean hasCustomName() {
        return this.getCustomName() != null;
    }

    default Component getDisplayName() {
        return this.getName();
    }

    @Nullable
    default Component getCustomName() {
        return null;
    }
}