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First version of Iterator vs For Loop unit testing (#15365)

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* First version of Iterator vs For Loop unit testing

* Add a new line after package

* Update the method name
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Wynn Teo 2023-12-23 10:27:39 +08:00 committed by GitHub
parent fcb652319b
commit 4b6c1c6e05
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core-java-modules/core-java-collections-5/src/test/java/com/baeldung/iteratorvsforloop/IteratorForLoopUnitTest.java Normal file
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package com.baeldung.iteratorvsforloop;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.ConcurrentModificationException;
import java.util.List;
import java.util.Iterator;
import java.util.Collections;
import java.util.ListIterator;
public class IteratorForLoopUnitTest {
@Test
public void givenEmptyCollection_whenUsingForLoop_thenNoElementsAreIterated() {
List<String> names = Collections.emptyList();
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i < names.size(); i++) {
stringBuilder.append(names.get(i));
}
assertEquals("", stringBuilder.toString());
}
@Test
public void givenEmptyCollection_whenUsingIterator_thenNoElementsAreIterated() {
List<String> names = Collections.emptyList();
StringBuilder stringBuilder = new StringBuilder();
Iterator<String> iterator = names.iterator();
while (iterator.hasNext()) {
stringBuilder.append(iterator.next());
}
assertEquals("", stringBuilder.toString());
}
@Test
public void givenCollectionWithElements_whenUsingForLoop_thenAllElementsAreIterated() {
List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i < names.size(); i++) {
stringBuilder.append(names.get(i));
}
assertEquals("AliceBobCharlie", stringBuilder.toString());
}
@Test
public void givenCollectionWithElements_whenUsingIterator_thenAllElementsAreIterated() {
List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
StringBuilder stringBuilder = new StringBuilder();
Iterator<String> iterator = names.iterator();
while (iterator.hasNext()) {
stringBuilder.append(iterator.next());
}
assertEquals("AliceBobCharlie", stringBuilder.toString());
}
@Test
public void givenCollectionWithElements_whenUsingForLoop_thenAllElementsAreIteratedReverseOrder() {
List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
StringBuilder stringBuilder = new StringBuilder();
for (int i = names.size() - 1; i >= 0; i--) {
stringBuilder.append(names.get(i));
}
assertEquals("CharlieBobAlice", stringBuilder.toString());
}
@Test
public void givenCollectionWithElements_whenUsingListIterator_thenAllElementsAreIteratedInReverseOrder() {
List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
StringBuilder stringBuilder = new StringBuilder();
ListIterator<String> listIterator = names.listIterator(names.size());
while (listIterator.hasPrevious()) {
stringBuilder.append(listIterator.previous());
}
assertEquals("CharlieBobAlice", stringBuilder.toString());
}
@Test
public void givenCollectionWithElements_whenRemovingElementDuringForLoopIteration_thenConcurrentModificationExceptionIsThrown() {
List<String> names = new ArrayList<>(List.of("Alice", "Bob", "Charlie"));
assertThrows(ConcurrentModificationException.class, () -> {
for (String name : names) {
names.remove("Bob");
}
});
}
@Test
public void givenCollectionWithElements_whenRemovingElementUsingIterator_thenElementIsRemovedSafely() {
List<String> names = new ArrayList<>(Arrays.asList("Alice", "Bob", "Charlie"));
Iterator<String> iterator = names.iterator();
while (iterator.hasNext()) {
String name = iterator.next();
if (name.equals("Bob")) {
iterator.remove();
}
}
List<String> expected = Arrays.asList("Alice", "Charlie");
assertIterableEquals(expected, names);
}
@Test
public void givenCollectionWithElements_whenModifyingElementToLowerCaseDuringForLoopIteration_thenElementsAreModifiedToLowerCase() {
List<String> names = new ArrayList<>(List.of("Alice", "Bob", "Charlie"));
for (int i = 0; i < names.size(); i++) {
names.set(i, names.get(i).toLowerCase());
}
List<String> expected = Arrays.asList("alice","bob", "charlie");
assertIterableEquals(expected, names);
}
}