ImmutableSetClient.java

package trial.yy.guava.client.collect;

import com.google.common.collect.ImmutableSet;

import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.Set;

/**
 * com.google.common.collect.ImmutableSetを試すためのサンプル
 * User: yy
 */
public class ImmutableSetClient {

    public static void main(String[] args) {

        // Collections#unmodifiableSetとImmutableSet#copyOfで生成したSetの動きの違いを確認
        System.out.println("### Difference between Collections#unmodifiableSet and ImmutableSet#copyOf");
        Set<String> names = new LinkedHashSet<>();
        names.add("taro");
        names.add("jiro");

        Set<String> setBuiltIn = Collections.unmodifiableSet(names);
        Set<String> setGuava = ImmutableSet.copyOf(names);

        names.add("saburo");

        // 生成元のSetに対して要素を追加してもImmutableSetには追加されない
        System.out.println("Built In Set: " + setBuiltIn);    // ->  [taro, jiro, saburo]
        System.out.println("Guava Set: " + setGuava);         // ->  [taro, jiro]

        System.out.println("### ImmutableSet#of");
        ImmutableSet<Integer> set1 = ImmutableSet.of(1, 2, 3, 4);
        try {
            set1.add(5);
        } catch (UnsupportedOperationException e) {
            e.printStackTrace();
        }
        System.out.println("set1: " + set1);

        // ImmutableSet.Builderを使って元のSet＋新しい要素のImmutableSetを生成
        System.out.println("### ImmutableSet.Builder#build");
        Set<String> set = ImmutableSet.of("ABC", "DEF", "GHI");
        ImmutableSet<String> setStrGuava = new ImmutableSet.Builder<String>()
                        .addAll(set)
                        .add("JKL")
                        .build();
        System.out.println("setStrGuava: " + setStrGuava);
    }
}