Java : List (リスト) - API使用例
List (Java SE 21 & JDK 21) の使用例まとめです。
だいたいのメソッドを網羅済みです。
API仕様書のおともにどうぞ。
概要
List は順序付けされたコレクションです。
要素を追加するたびに 0, 1, 2, 3 ... とインデックスが割り振られて、厳密に順序が管理されます。
配列と似ていますが、配列と違いサイズを気にしなくてよいのが List の大きなメリットです。
List の基本は下記の記事にもまとめています。
そちらも参考にしていただければ幸いです。
final List<String> list = new ArrayList<>();
System.out.println(list); // []
list.add("aaa");
list.add("bbb");
list.add("ccc");
System.out.println(list); // [aaa, bbb, ccc]
System.out.println(list.get(0)); // aaa
System.out.println(list.get(1)); // bbb
System.out.println(list.get(2)); // ccc
メソッド
void add (int index, E element)
final var src = List.of("a", "b", "c");
System.out.println(src); // [a, b, c]
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
list.add(0, "A");
System.out.println(list); // [A, a, b, c]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
list.add(1, "B");
System.out.println(list); // [a, B, b, c]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
list.add(2, "C");
System.out.println(list); // [a, b, C, c]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
list.add(3, "D");
System.out.println(list); // [a, b, c, D]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
try {
list.add(4, "E");
} catch (IndexOutOfBoundsException e) {
System.out.println("IndexOutOfBoundsException!");
}
// 結果
// ↓
//IndexOutOfBoundsException!
}
boolean add (E e)
final List<String> list = new ArrayList<>();
System.out.println(list); // []
System.out.println(list.add("a")); // true
System.out.println(list); // [a]
System.out.println(list.add("b")); // true
System.out.println(list); // [a, b]
System.out.println(list.add("c")); // true
System.out.println(list); // [a, b, c]
boolean addAll (int index, Collection<? extends E> c)
final var src = List.of("a", "b", "c");
System.out.println(src); // [a, b, c]
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
System.out.println(list.addAll(0, List.of("A1", "A2"))); // true
System.out.println(list); // [A1, A2, a, b, c]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
System.out.println(list.addAll(1, List.of("B1", "B2", "B3"))); // true
System.out.println(list); // [a, B1, B2, B3, b, c]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
System.out.println(list.addAll(2, List.of("C1", "C2", "C3", "C4"))); // true
System.out.println(list); // [a, b, C1, C2, C3, C4, c]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
System.out.println(list.addAll(3, List.of())); // false
System.out.println(list); // [a, b, c]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
try {
list.addAll(4, List.of("E"));
} catch (IndexOutOfBoundsException e) {
System.out.println("IndexOutOfBoundsException!");
}
// 結果
// ↓
//IndexOutOfBoundsException!
}
final var src = List.of("a", "b", "c");
System.out.println(src);// [a, b, c]
final List<String> list = new ArrayList<>(src);
// Setは順序が保証されません。
System.out.println(list.addAll(3, Set.of("D1", "D2", "D3"))); // true
System.out.println(list); // [a, b, c, D3, D2, D1]
boolean addAll (Collection<? extends E> c)
final List<String> list = new ArrayList<>();
System.out.println(list.addAll(List.of("a1"))); // true
System.out.println(list); // [a1]
System.out.println(list.addAll(List.of("b1", "b2"))); // true
System.out.println(list); // [a1, b1, b2]
System.out.println(list.addAll(List.of("c1", "c2", "c3"))); // true
System.out.println(list); // [a1, b1, b2, c1, c2, c3]
System.out.println(list.addAll(List.of())); // false
System.out.println(list); // [a1, b1, b2, c1, c2, c3]
final List<String> list = new ArrayList<>();
System.out.println(list); // []
// Setは順序が保証されません。
System.out.println(list.addAll(Set.of("c1", "c2", "c3"))); // true
System.out.println(list); // [c3, c2, c1]
default void addFirst (E e)
final List<String> list = new ArrayList<>();
list.addFirst("aaa");
System.out.println(list); // [aaa]
list.addFirst("bbb");
System.out.println(list); // [bbb, aaa]
list.addFirst("ccc");
System.out.println(list); // [ccc, bbb, aaa]
default void addLast (E e)
final List<String> list = new ArrayList<>();
list.addLast("aaa");
System.out.println(list); // [aaa]
list.addLast("bbb");
System.out.println(list); // [aaa, bbb]
list.addLast("ccc");
System.out.println(list); // [aaa, bbb, ccc]
void clear ()
final List<String> list = new ArrayList<>();
list.add("a");
list.add("b");
list.add("c");
System.out.println(list); // [a, b, c]
list.clear();
System.out.println(list); // []
boolean contains (Object o)
final var list = List.of("a", "b", "c");
System.out.println(list); // [a, b, c]
System.out.println(list.contains("")); // false
System.out.println(list.contains("a")); // true
System.out.println(list.contains("b")); // true
System.out.println(list.contains("c")); // true
System.out.println(list.contains("abc")); // false
boolean containsAll (Collection<?> c)
final var list = List.of("a", "b", "c");
System.out.println(list); // [a, b, c]
System.out.println(list.containsAll(List.<String>of())); // true
System.out.println(list.containsAll(List.of("a"))); // true
System.out.println(list.containsAll(List.of("a", "b"))); // true
System.out.println(list.containsAll(List.of("b", "a"))); // true
System.out.println(list.containsAll(List.of("c", "b", "a"))); // true
System.out.println(list.containsAll(List.of("d"))); // false
System.out.println(list.containsAll(List.of("a", "d"))); // false
System.out.println(list.containsAll(List.of("a", "b", "c", "d"))); // false
static <E> List<E> copyOf (Collection<? extends E> coll)
final List<String> list = new ArrayList<>();
list.add("a");
list.add("b");
list.add("c");
System.out.println(list); // [a, b, c]
final var copiedList = List.copyOf(list);
System.out.println(copiedList); // [a, b, c]
list.clear();
System.out.println(list); // []
System.out.println(copiedList); // [a, b, c]
try {
copiedList.add("d");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
boolean equals (Object o)
final var list = List.of("a", "b", "c");
System.out.println(list); // [a, b, c]
System.out.println(list.equals(List.of("a"))); // false
System.out.println(list.equals(List.of("a", "b"))); // false
System.out.println(list.equals(List.of("a", "b", "c"))); // true
System.out.println(list.equals(List.of("c", "b", "a"))); // false
final var list = List.of("a", "b", "c");
System.out.println(list); // [a, b, c]
final var arrayList = new ArrayList<>(list);
System.out.println(arrayList); // [a, b, c]
System.out.println(list.equals(arrayList)); // true
final var linkedList = new LinkedList<>(list);
System.out.println(linkedList); // [a, b, c]
System.out.println(list.equals(linkedList)); // true
final var list = List.of("a", "b", "c");
System.out.println(list); // [a, b, c]
final var set = new LinkedHashSet<>();
set.add("a");
set.add("b");
set.add("c");
System.out.println(set); // [a, b, c]
System.out.println(list.equals(set)); // false
E get (int index)
final var list = List.of("a", "b", "c");
System.out.println(list); // [a, b, c]
//list.get(-1); // IndexOutOfBoundsException
System.out.println(list.get(0)); // a
System.out.println(list.get(1)); // b
System.out.println(list.get(2)); // c
//list.get(3); // IndexOutOfBoundsException
final var list = List.of(10, 20, 30, 40);
System.out.println(list); // [10, 20, 30, 40]
System.out.println(list.get(0)); // 10
System.out.println(list.get(1)); // 20
System.out.println(list.get(2)); // 30
System.out.println(list.get(3)); // 40
default E getFirst ()
final List<String> list = new ArrayList<>();
list.addLast("aaa");
System.out.println(list); // [aaa]
System.out.println(list.getFirst()); // aaa
list.addLast("bbb");
System.out.println(list); // [aaa, bbb]
System.out.println(list.getFirst()); // aaa
list.addLast("ccc");
System.out.println(list); // [aaa, bbb, ccc]
System.out.println(list.getFirst()); // aaa
final List<String> list = new ArrayList<>();
System.out.println(list); // []
try {
final var ret = list.getFirst();
} catch (NoSuchElementException e) {
System.out.println("NoSuchElementException!");
}
// 結果
// ↓
//NoSuchElementException!
default E getLast ()
final List<String> list = new ArrayList<>();
list.addLast("aaa");
System.out.println(list); // [aaa]
System.out.println(list.getLast()); // aaa
list.addLast("bbb");
System.out.println(list); // [aaa, bbb]
System.out.println(list.getLast()); // bbb
list.addLast("ccc");
System.out.println(list); // [aaa, bbb, ccc]
System.out.println(list.getLast()); // ccc
final List<String> list = new ArrayList<>();
System.out.println(list); // []
try {
final var ret = list.getLast();
} catch (NoSuchElementException e) {
System.out.println("NoSuchElementException!");
}
// 結果
// ↓
//NoSuchElementException!
int hashCode ()
final var list1 = List.of("a", "b", "c");
System.out.println(list1.hashCode()); // 126145
final var list2 = List.of("A", "B", "C");
System.out.println(list2.hashCode()); // 94369
final var list3 = List.of(1, 2, 3);
System.out.println(list3.hashCode()); // 30817
int indexOf (Object o)
final var list = List.of("a", "b", "c", "a", "b", "c");
System.out.println(list); // [a, b, c, a, b, c]
System.out.println(list.indexOf("")); // -1
System.out.println(list.indexOf("a")); // 0
System.out.println(list.indexOf("b")); // 1
System.out.println(list.indexOf("c")); // 2
System.out.println(list.indexOf("d")); // -1
System.out.println(list.indexOf("abc")); // -1
boolean isEmpty ()
final List<String> list = new ArrayList<>();
list.add("a");
list.add("b");
list.add("c");
System.out.println(list); // [a, b, c]
System.out.println(list.isEmpty()); // false
list.clear();
System.out.println(list); // []
System.out.println(list.isEmpty()); // true
Iterator<E> iterator ()
final var list = List.of("aaa", "bbb", "ccc");
System.out.println(list); // [aaa, bbb, ccc]
final var iterator = list.iterator();
iterator.forEachRemaining(System.out::println);
// 結果
// ↓
//aaa
//bbb
//ccc
int lastIndexOf (Object o)
final var list = List.of("a", "b", "c", "a", "b", "c");
System.out.println(list); // [a, b, c, a, b, c]
System.out.println(list.lastIndexOf("")); // -1
System.out.println(list.lastIndexOf("a")); // 3
System.out.println(list.lastIndexOf("b")); // 4
System.out.println(list.lastIndexOf("c")); // 5
System.out.println(list.lastIndexOf("d")); // -1
System.out.println(list.lastIndexOf("abc")); // -1
ListIterator<E> listIterator ()
final var list = List.of("aaa", "bbb", "ccc");
System.out.println(list); // [aaa, bbb, ccc]
final var listIterator = list.listIterator();
listIterator.forEachRemaining(System.out::println);
// 結果
// ↓
//aaa
//bbb
//ccc
ListIterator<E> listIterator (int index)
final var list = List.of("aaa", "bbb", "ccc");
System.out.println(list); // [aaa, bbb, ccc]
{
final var ret = list.listIterator(0);
ret.forEachRemaining(System.out::println);
// 結果
// ↓
//aaa
//bbb
//ccc
}
{
final var ret = list.listIterator(1);
ret.forEachRemaining(System.out::println);
// 結果
// ↓
//bbb
//ccc
}
{
final var ret = list.listIterator(2);
ret.forEachRemaining(System.out::println);
// 結果
// ↓
//ccc
}
static <E> List<E> of ()
final var list = List.of();
System.out.println(list); // []
System.out.println(list.size()); // 0
try {
list.add("a");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
static <E> List<E> of (E e1)
final var list = List.of("a");
System.out.println(list); // [a]
System.out.println(list.size()); // 1
try {
list.add("b");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
static <E> List<E> of (E... elements)
final var list = List.of(
"a", "b", "c", "d", "e", "f", "g", "h", "i", "j",
"k", "l", "m", "n"
);
System.out.println(list); // [a, b, c, d, e, f, g, h, i, j, k, l, m, n]
System.out.println(list.size()); // 14
try {
list.add("z");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
static <E> List<E> of (E e1, E e2)
final var list = List.of("a", "b");
System.out.println(list); // [a, b]
System.out.println(list.size()); // 2
try {
list.add("z");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
static <E> List<E> of (E e1, E e2, E e3)
final var list = List.of("a", "b", "c");
System.out.println(list); // [a, b, c]
System.out.println(list.size()); // 3
try {
list.add("z");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
static <E> List<E> of (E e1, E e2, E e3, E e4)
final var list = List.of("a", "b", "c", "d");
System.out.println(list); // [a, b, c, d]
System.out.println(list.size()); // 4
try {
list.add("z");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
static <E> List<E> of (E e1, E e2, E e3, E e4, E e5)
final var list = List.of("a", "b", "c", "d", "e");
System.out.println(list); // [a, b, c, d, e]
System.out.println(list.size()); // 5
try {
list.add("z");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
static <E> List<E> of (E e1, E e2, E e3, E e4, E e5, E e6)
final var list = List.of("a", "b", "c", "d", "e", "f");
System.out.println(list); // [a, b, c, d, e, f]
System.out.println(list.size()); // 6
try {
list.add("z");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
static <E> List<E> of (E e1, E e2, E e3, E e4, E e5, E e6, E e7)
final var list = List.of("a", "b", "c", "d", "e", "f", "g");
System.out.println(list); // [a, b, c, d, e, f, g]
System.out.println(list.size()); // 7
try {
list.add("z");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
static <E> List<E> of (E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8)
final var list = List.of("a", "b", "c", "d", "e", "f", "g", "h");
System.out.println(list); // [a, b, c, d, e, f, g, h]
System.out.println(list.size()); // 8
try {
list.add("z");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
static <E> List<E> of (E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9)
final var list = List.of("a", "b", "c", "d", "e", "f", "g", "h", "i");
System.out.println(list); // [a, b, c, d, e, f, g, h, i]
System.out.println(list.size()); // 9
try {
list.add("z");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
static <E> List<E> of (E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10)
final var list = List.of("a", "b", "c", "d", "e", "f", "g", "h", "i", "j");
System.out.println(list); // [a, b, c, d, e, f, g, h, i, j]
System.out.println(list.size()); // 10
try {
list.add("z");
} catch (UnsupportedOperationException e) {
System.out.println("UnsupportedOperationException!");
}
// 結果
// ↓
//UnsupportedOperationException!
E remove (int index)
final var src = List.of("a", "b", "c");
System.out.println(src); // [a, b, c]
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
System.out.println(list.remove(0)); // a
System.out.println(list); // [b, c]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
System.out.println(list.remove(1)); // b
System.out.println(list); // [a, c]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
System.out.println(list.remove(2)); // c
System.out.println(list); // [a, b]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
try {
list.remove(3);
} catch (IndexOutOfBoundsException e) {
System.out.println("IndexOutOfBoundsException!");
}
// 結果
// ↓
//IndexOutOfBoundsException!
}
boolean remove (Object o)
final var src = List.of("a", "b", "a", "b", "A", "B");
System.out.println(src); // [a, b, a, b, A, B]
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.remove("")); // false
System.out.println(list); // [a, b, a, b, A, B]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.remove("a")); // true
System.out.println(list); // [b, a, b, A, B]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.remove("b")); // true
System.out.println(list); // [a, a, b, A, B]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.remove("A")); // true
System.out.println(list); // [a, b, a, b, B]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.remove("B")); // true
System.out.println(list); // [a, b, a, b, A]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.remove("C")); // false
System.out.println(list); // [a, b, a, b, A, B]
}
boolean removeAll (Collection<?> c)
final var src = List.of("a", "b", "a", "b", "A", "B");
System.out.println(src); // [a, b, a, b, A, B]
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.removeAll(List.<String>of())); // false
System.out.println(list); // [a, b, a, b, A, B]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.removeAll(List.of("a"))); // true
System.out.println(list); // [b, b, A, B]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.removeAll(List.of("a", "b"))); // true
System.out.println(list); // [A, B]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.removeAll(List.of("b", "a"))); // true
System.out.println(list); // [A, B]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.removeAll(List.of("A"))); // true
System.out.println(list); // [a, b, a, b, B]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.removeAll(List.of("X", "Y", "Z"))); // false
System.out.println(list); // [a, b, a, b, A, B]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.removeAll(List.of("A", "X", "Y", "Z"))); // true
System.out.println(list); // [a, b, a, b, B]
}
default E removeFirst ()
final List<String> list = new ArrayList<>();
list.addLast("aaa");
list.addLast("bbb");
list.addLast("ccc");
System.out.println(list); // [aaa, bbb, ccc]
System.out.println(list.removeFirst()); // aaa
System.out.println(list); // [bbb, ccc]
System.out.println(list.removeFirst()); // bbb
System.out.println(list); // [ccc]
System.out.println(list.removeFirst()); // ccc
System.out.println(list); // []
final List<String> list = new ArrayList<>();
System.out.println(list); // []
try {
final var ret = list.removeFirst();
} catch (NoSuchElementException e) {
System.out.println("NoSuchElementException!");
}
// 結果
// ↓
//NoSuchElementException!
default E removeLast ()
final List<String> list = new ArrayList<>();
list.addLast("aaa");
list.addLast("bbb");
list.addLast("ccc");
System.out.println(list); // [aaa, bbb, ccc]
System.out.println(list.removeLast()); // ccc
System.out.println(list); // [aaa, bbb]
System.out.println(list.removeLast()); // bbb
System.out.println(list); // [aaa]
System.out.println(list.removeLast()); // aaa
System.out.println(list); // []
final List<String> list = new ArrayList<>();
System.out.println(list); // []
try {
final var ret = list.removeLast();
} catch (NoSuchElementException e) {
System.out.println("NoSuchElementException!");
}
// 結果
// ↓
//NoSuchElementException!
default void replaceAll (UnaryOperator<E> operator)
final List<String> list = new ArrayList<>();
list.add("a");
list.add("b");
list.add("a");
list.add("b");
System.out.println(list); // [a, b, a, b]
list.replaceAll(String::toUpperCase);
System.out.println(list); // [A, B, A, B]
final List<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
list.add(3);
list.add(4);
System.out.println(list); // [1, 2, 3, 4]
list.replaceAll(num -> num * num);
System.out.println(list); // [1, 4, 9, 16]
boolean retainAll (Collection<?> c)
final var src = List.of("a", "b", "a", "b", "A", "B");
System.out.println(src); // [a, b, a, b, A, B]
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.retainAll(List.<String>of())); // true
System.out.println(list); // []
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.retainAll(List.of("a", "b"))); // true
System.out.println(list); // [a, b, a, b]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.retainAll(List.of("b", "a"))); // true
System.out.println(list); // [a, b, a, b]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.retainAll(List.of("A"))); // true
System.out.println(list); // [A]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.retainAll(List.of("X", "Y", "Z"))); // true
System.out.println(list); // []
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.retainAll(List.of("A", "X", "Y", "Z"))); // true
System.out.println(list); // [A]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, a, b, A, B]
System.out.println(list.retainAll(List.of("a", "b", "A", "B"))); // false
System.out.println(list); // [a, b, a, b, A, B]
}
default List<E> reversed ()
final List<String> list = new ArrayList<>();
list.addLast("aaa");
list.addLast("bbb");
list.addLast("ccc");
System.out.println(list); // [aaa, bbb, ccc]
final var reversedSc = list.reversed();
System.out.println(reversedSc); // [ccc, bbb, aaa]
System.out.println(reversedSc.reversed()); // [aaa, bbb, ccc]
E set (int index, E element)
final var src = List.of("a", "b", "c");
System.out.println(src); // [a, b, c]
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
System.out.println(list.set(0, "A")); // a
System.out.println(list); // [A, b, c]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
System.out.println(list.set(1, "B")); // b
System.out.println(list); // [a, B, c]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
System.out.println(list.set(2, "C")); // c
System.out.println(list); // [a, b, C]
}
{
final List<String> list = new ArrayList<>(src);
System.out.println(list); // [a, b, c]
try {
list.set(3, "D");
} catch (IndexOutOfBoundsException e) {
System.out.println("IndexOutOfBoundsException!");
}
// 結果
// ↓
//IndexOutOfBoundsException!
}
int size ()
final var list1 = List.of();
System.out.println(list1); // []
System.out.println(list1.size()); // 0
final var list2 = List.of("a", "b", "c", "X", "Y", "Z");
System.out.println(list2); // [a, b, c, X, Y, Z]
System.out.println(list2.size()); // 6
default void sort (Comparator<? super E> c)
final var src = List.of(2, 3, 1, 4);
{
final List<Integer> list = new ArrayList<>(src);
list.sort(null);
System.out.println(list); // [1, 2, 3, 4]
}
{
final List<Integer> list = new ArrayList<>(src);
list.sort(Comparator.reverseOrder());
System.out.println(list); // [4, 3, 2, 1]
}
default Spliterator<E> spliterator ()
final var list = List.of("aaa", "bbb", "ccc");
System.out.println(list); // [aaa, bbb, ccc]
final var spliterator = list.spliterator();
spliterator.forEachRemaining(System.out::println);
// 結果
// ↓
//aaa
//bbb
//ccc
List<E> subList (int fromIndex, int toIndex)
final List<String> list = new ArrayList<>();
list.add("a");
list.add("b");
list.add("c");
list.add("d");
System.out.println(list); // [a, b, c, d]
System.out.println(list.subList(0, 0)); // []
System.out.println(list.subList(0, 1)); // [a]
System.out.println(list.subList(0, 2)); // [a, b]
System.out.println(list.subList(0, 3)); // [a, b, c]
System.out.println(list.subList(0, 4)); // [a, b, c, d]
//list.subList(0, 5); // IndexOutOfBoundsException
final var subList = list.subList(1, 3);
System.out.println(subList); // [b, c]
System.out.println(list); // [a, b, c, d]
subList.set(0, "X");
System.out.println(subList); // [X, c]
System.out.println(list); // [a, X, c, d]
subList.add("Y");
System.out.println(subList); // [X, c, Y]
System.out.println(list); // [a, X, c, Y, d]
subList.remove("c");
System.out.println(subList); // [X, Y]
System.out.println(list); // [a, X, Y, d]
Object[] toArray ()
final var list = List.of("a", "b", "c");
System.out.println(list); // [a, b, c]
final Object[] array = list.toArray();
System.out.println(Arrays.toString(array)); // [a, b, c]
<T> T[] toArray (T[] a)
final var list = List.of("a", "b", "c");
System.out.println(list); // [a, b, c]
final String[] array = list.toArray(new String[0]);
System.out.println(Arrays.toString(array)); // [a, b, c]
final var list = List.of("a", "b", "c");
System.out.println(list); // [a, b, c]
{
final String[] array = new String[3];
System.out.println(Arrays.toString(array)); // [null, null, null]
final var ret = list.toArray(array);
System.out.println(Arrays.toString(array)); // [a, b, c]
System.out.println(Arrays.toString(ret)); // [a, b, c]
}
{
final String[] array = new String[5];
System.out.println(Arrays.toString(array)); // [null, null, null, null, null]
final var ret = list.toArray(array);
System.out.println(Arrays.toString(array)); // [a, b, c, null, null]
System.out.println(Arrays.toString(ret)); // [a, b, c, null, null]
}
{
final String[] array = new String[1];
System.out.println(Arrays.toString(array)); // [null]
final var ret = list.toArray(array);
System.out.println(Arrays.toString(array)); // [null]
System.out.println(Arrays.toString(ret)); // [a, b, c]
}
Collectionで宣言されたメソッド
parallelStream, removeIf, stream, toArray
「Java API 使用例 : Collection」をご参照ください。
Iterableで宣言されたメソッド
forEach
「Java API 使用例 : Iterable」をご参照ください。
関連記事
- List(リスト)の基本
- Map(マップ)の基本
- Set(セット)の基本
- List の初期化方法いろいろ
- Map の初期化方法いろいろ
- 配列 vs. List
- 配列からListへの変換
- List から配列への変換
- API 使用例
- Collection (コレクション)
- Collections (コレクション操作)
- Comparable
- Comparator
- Iterator
- List (リスト)
- Map (マップ)
- Map.Entry (キーと値のペア)
- Queue (キュー)
- AbstractQueue
- ArrayBlockingQueue (ブロッキング・配列キュー)
- ArrayDeque (両端キュー)
- BlockingDeque (ブロッキング・両端キュー)
- BlockingQueue (ブロッキング・キュー)
- ConcurrentLinkedDeque (並列処理用・両端キュー)
- ConcurrentLinkedQueue (並列処理用キュー)
- Deque (両端キュー)
- LinkedBlockingDeque (ブロッキング・リンク両端キュー)
- LinkedBlockingQueue (ブロッキング・リンクキュー)
- LinkedList (二重リンク・リスト)
- PriorityBlockingQueue (ブロッキング・優先度付きキュー)
- PriorityQueue (優先度付きキュー)
- RandomAccess
- Set (セット)
- Spliterator