Merge pull request #1837 from fabriciofx/1836

#1836: Implements Immutable Set

Author: yegor256

src/main/java/org/cactoos/set/Immutable.java

@@ -0,0 +1,125 @@
+/*
+ * SPDX-FileCopyrightText: Copyright (c) 2017-2026 Yegor Bugayenko
+ * SPDX-License-Identifier: MIT
+ */
+package org.cactoos.set;
+
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Set;
+
+/**
+ * Decorator that doesn't allow mutations of the wrapped {@link Set}.
+ *
+ * <p>There is no thread-safety guarantee.</p>
+ *
+ * @param <T> Element type
+ * @since 0.58.0
+ */
+@SuppressWarnings("PMD.TooManyMethods")
+public final class Immutable<T> implements Set<T> {
+    /**
+     * Encapsulated set.
+     */
+    private final Set<? extends T> set;
+
+    /**
+     * Ctor.
+     * @param src Source set
+     */
+    public Immutable(final Set<? extends T> src) {
+        this.set = src;
+    }
+
+    @Override
+    public int size() {
+        return this.set.size();
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return this.set.isEmpty();
+    }
+
+    @Override
+    public boolean contains(final Object item) {
+        return this.set.contains(item);
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+        return new org.cactoos.iterator.Immutable<>(this.set.iterator());
+    }
+
+    @Override
+    public Object[] toArray() {
+        return this.set.toArray();
+    }
+
+    @Override
+    public <X> X[] toArray(final X[] array) {
+        return this.set.toArray(array);
+    }
+
+    @Override
+    public boolean add(final T item) {
+        throw new UnsupportedOperationException(
+            "#add(T): the set is read-only"
+        );
+    }
+
+    @Override
+    public boolean remove(final Object item) {
+        throw new UnsupportedOperationException(
+            "#remove(Object): the set is read-only"
+        );
+    }
+
+    @Override
+    public boolean containsAll(final Collection<?> items) {
+        return this.set.containsAll(items);
+    }
+
+    @Override
+    public boolean addAll(final Collection<? extends T> items) {
+        throw new UnsupportedOperationException(
+            "#addAll(Collection): the set is read-only"
+        );
+    }
+
+    @Override
+    public boolean retainAll(final Collection<?> items) {
+        throw new UnsupportedOperationException(
+            "#retainAll(Collection): the set is read-only"
+        );
+    }
+
+    @Override
+    public boolean removeAll(final Collection<?> items) {
+        throw new UnsupportedOperationException(
+            "#removeAll(Collection): the set is read-only"
+        );
+    }
+
+    @Override
+    public void clear() {
+        throw new UnsupportedOperationException(
+            "#clear(): the set is read-only"
+        );
+    }
+
+    @Override
+    public boolean equals(final Object other) {
+        return this.set.equals(other);
+    }
+
+    @Override
+    public int hashCode() {
+        return this.set.hashCode();
+    }
+
+    @Override
+    public String toString() {
+        return this.set.toString();
+    }
+}

src/test/java/org/cactoos/io/ReaderOfTest.java

@@ -262,7 +262,7 @@ void readsCharSequenceWithCharset() {
         final String input =
             "char sequence with charset on äÄ üÜ öÖ ß жш";
         new Assertion<>(
-            "Must read from char sequance with charset",
+            "Must read from char sequence with charset",
             new TextOf(
                 new ReaderOf(
                     input,