BAEL-2403: Immutable Map implementations in Java (#5828)
* BAEL-2203 - Convert java.time.Instant to java.sql.Timestamp and vice-versa * BAEL-2203: Review edits * Removed ZoneId code * Converted class to JUnit Test * Update and rename ConvertInstantToTimestampTest.java to ConvertInstantToTimestampUnitTest.java * BAEL-2403: Immutable Map implementations in Java * BAEL-2403: Immutable Map implementations in Java - Changed file name
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package com.baeldung.java.map;
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import static org.junit.jupiter.api.Assertions.assertFalse;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.Map;
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import org.junit.jupiter.api.Test;
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import com.google.common.collect.ImmutableMap;
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public class ImmutableMapUnitTest {
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@Test
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public void whenCollectionsUnModifiableMapMethod_thenOriginalCollectionChangesReflectInUnmodifiableMap() {
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Map<String, String> mutableMap = new HashMap<>();
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mutableMap.put("USA", "North America");
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Map<String, String> unmodifiableMap = Collections.unmodifiableMap(mutableMap);
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assertThrows(UnsupportedOperationException.class, () -> unmodifiableMap.put("Canada", "North America"));
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mutableMap.remove("USA");
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assertFalse(unmodifiableMap.containsKey("USA"));
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mutableMap.put("Mexico", "North America");
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assertTrue(unmodifiableMap.containsKey("Mexico"));
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}
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@Test
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@SuppressWarnings("deprecation")
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public void whenGuavaImmutableMapFromCopyOfMethod_thenOriginalCollectionChangesDoNotReflectInImmutableMap() {
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Map<String, String> mutableMap = new HashMap<>();
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mutableMap.put("USA", "North America");
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ImmutableMap<String, String> immutableMap = ImmutableMap.copyOf(mutableMap);
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assertTrue(immutableMap.containsKey("USA"));
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assertThrows(UnsupportedOperationException.class, () -> immutableMap.put("Canada", "North America"));
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mutableMap.remove("USA");
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assertTrue(immutableMap.containsKey("USA"));
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mutableMap.put("Mexico", "North America");
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assertFalse(immutableMap.containsKey("Mexico"));
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}
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@Test
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@SuppressWarnings("deprecation")
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public void whenGuavaImmutableMapFromBuilderMethod_thenOriginalCollectionChangesDoNotReflectInImmutableMap() {
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Map<String, String> mutableMap = new HashMap<>();
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mutableMap.put("USA", "North America");
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ImmutableMap<String, String> immutableMap = ImmutableMap.<String, String>builder()
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.putAll(mutableMap)
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.put("Costa Rica", "North America")
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.build();
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assertTrue(immutableMap.containsKey("USA"));
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assertTrue(immutableMap.containsKey("Costa Rica"));
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assertThrows(UnsupportedOperationException.class, () -> immutableMap.put("Canada", "North America"));
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mutableMap.remove("USA");
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assertTrue(immutableMap.containsKey("USA"));
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mutableMap.put("Mexico", "North America");
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assertFalse(immutableMap.containsKey("Mexico"));
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}
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@Test
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@SuppressWarnings("deprecation")
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public void whenGuavaImmutableMapFromOfMethod_thenOriginalCollectionChangesDoNotReflectInImmutableMap() {
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ImmutableMap<String, String> immutableMap = ImmutableMap.of("USA", "North America", "Costa Rica", "North America");
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assertTrue(immutableMap.containsKey("USA"));
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assertTrue(immutableMap.containsKey("Costa Rica"));
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assertThrows(UnsupportedOperationException.class, () -> immutableMap.put("Canada", "North America"));
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}
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}
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