Java 集合

Java 集合

集合/容器

Collection

Map

Collection

Map

Collection

Collection

List

Queue

Set

boolean add(E e)

boolean    addAll(Collection<? extends E> c)

void clear()

boolean    remove(Object o)

boolean    removeAll(Collection<?> c)

boolean    retainAll(Collection<?> c)

boolean contains(Object o)

boolean containsAll(Collection<?> c)

Iterator<E>    iterator()

Object[]   toArray()

<T> T[]    toArray(T[] a)

boolean    isEmpty()

int    size()

Iterator

iterator()

Iterator

Iterator

Iterator

boolean hasNext()

E next()

void remove()

Collection

Collection

remove

Iterator

remove

/**
* @author jifang
* @since 16/1/25 上午9:59.
*/
public class RemoveClient {

Collection<Integer> collection = new ArrayList<>();

@Before
public void setUp() {
Random random = new Random();
for (int i = 0; i < 10; ++i) {
collection.add(random.nextInt(i + 1));
}
}

@Test
public void client() {
System.out.print("before:");
for (Iterator<Integer> iterator = collection.iterator(); iterator.hasNext(); ) {
Integer integer = iterator.next();
System.out.printf(" %d", integer);
if (integer == 0) {
//collection.remove(i);
iterator.remove();
}
}
System.out.printf("%n after:");
for (Integer integer : collection) {
System.out.printf(" %d", integer);
}
}
}

foreach

foreach

Iterator

List

List

List

Collection

void add(int index, E element)

E    get(int index)

int  indexOf(Object o)

int  lastIndexOf(Object o)

E    remove(int index)

E    set(int index, E element)

List<E>  subList(int fromIndex, int toIndex)

List

equals()

public int indexOf(Object o) {
if (o == null) {
for (int i = 0; i < size; i++)
if (elementData[i]==null)
return i;
} else {
for (int i = 0; i < size; i++)
if (o.equals(elementData[i]))
return i;
}
return -1;
}

ListIterator

List

ListIterator

ListIterator<E>  listIterator()

ListIterator<E>  listIterator(int index)

ListIterator

Iterator

List

Iterator

void add(E e)

void set(E e)

boolean  hasPrevious()

E    previous()

int  previousIndex()

int  nextIndex()

Iterator

ArrayList

ArrayList

List

Object[]

/**
* The array buffer into which the elements of the ArrayList are stored.
* The capacity of the ArrayList is the length of this array buffer. Any
* empty ArrayList with elementData == EMPTY_ELEMENTDATA will be expanded to
* DEFAULT_CAPACITY when the first element is added.
*/
private transient Object[] elementData;

ArrayList

initialCapacity

ArrayList(int initialCapacity)

DEFAULT_CAPACITY = 10

elementData

ArrayList

/**
* Appends the specified element to the end of this list.
*
* @param e element to be appended to this list
* @return <tt>true</tt> (as specified by {@link Collection#add})
*/
public boolean add(E e) {
ensureCapacityInternal(size + 1);  // Increments modCount!!
elementData[size++] = e;
return true;
}

private void ensureCapacityInternal(int minCapacity) {
if (elementData == EMPTY_ELEMENTDATA) {
minCapacity = Math.max(DEFAULT_CAPACITY, minCapacity);
}

ensureExplicitCapacity(minCapacity);
}

private void ensureExplicitCapacity(int minCapacity) {
modCount++;

// overflow-conscious code
if (minCapacity - elementData.length > 0)
grow(minCapacity);
}

/**
* Increases the capacity to ensure that it can hold at least the
* number of elements specified by the minimum capacity argument.
*
* @param minCapacity the desired minimum capacity
*/
private void grow(int minCapacity) {
// overflow-conscious code
int oldCapacity = elementData.length;
int newCapacity = oldCapacity + (oldCapacity >> 1);
if (newCapacity - minCapacity < 0)
newCapacity = minCapacity;
if (newCapacity - MAX_ARRAY_SIZE > 0)
newCapacity = hugeCapacity(minCapacity);
// minCapacity is usually close to size, so this is a win:
elementData = Arrays.copyOf(elementData, newCapacity);
}

ArrayList

initialCapacity

ArrayList

initialCapacity

void ensureCapacity(int minCapacity)

void trimToSize()

Arrays

static

List<T> asList(T... a)

List

List

ArrayList

Arrays

Arrays.ArrayList

List

ArrayList

LinkedList

LinkedList

O(N)

O(1)

LinkedList

Deque

LinkedList

/**
* @author jifang
* @since 16/1/23 下午9:07.
*/
public class ListClient {

private Random random = new Random();

@Test
public void client() {
List<Integer> list = new LinkedList<>();
for (int i = 0; i < 10; ++i) {
list.add(random.nextInt(i + 1));
}

for (ListIterator<Integer> i = list.listIterator(); i.hasNext(); ) {
if (i.next() == 0) {
i.set(188);
i.add(-1);
}
}

System.out.println(list);
}
}

Queue

Queue

offer

poll

boolean  add(E e)

boolean  offer(E e)

E    element()

E    peek()

E    poll()

E    remove()

Queue

PriorityQueue

Queue

Deque

Deque

Stack

Deque

ArrayDeque

LinkedList

PriorityQueue

PriorityQueue

element/peek/poll/remove

/**
* @author jifang
* @since 16/1/28 下午6:20.
*/
public class QueueClient {

@Test
public void clientPriorityQueue() {

Random random = new Random();

Queue<Integer> queue = new PriorityQueue<>();
for (int i = 0; i < 10; ++i) {
queue.add(random.nextInt(100));
}

// 无序
System.out.print("iterator:");
for (Integer i : queue) {
System.out.printf(" %d", i);
}
System.out.println();

// 有序
System.out.print("pool:");
while (!queue.isEmpty()) {
System.out.printf(" %d", queue.poll());
}
System.out.println();
}
}

PriorityQueue

PriorityQueue

PriorityQueue

null

PriorityQueue

Comparable

PriorityQueue

Comparator

Comparable

TreeMap

Deque-ArrayDeque

Deque

Deque

ArrayDeque

LinkedList

ArrayDeque

E[] elements

numElements

elements

numElements

16

ArrayDeque

Deque

stack

@Test
public void asStack() {
Deque<Integer> stack = new ArrayDeque<>();

for (int i = 0; i < 10; ++i) {
stack.push(i);
}

while (!stack.isEmpty()) {
System.out.println(stack.pop());
}
}

LinkedList

Deque

Queue

Deque

Map

Map

key-value

key

value

key

value

V  put(K key, V value)

void   putAll(Map<? extends K,? extends V> m)

V  remove(Object key)

void   clear()

V  get(Object key)

Set<K> keySet()

Collection<V>  values()

Set<Map.Entry<K,V>>    entrySet()

boolean    containsKey(Object key)

boolean    containsValue(Object value)

boolean    isEmpty()

int    size()

Map

Map.Entry<K,V>

key-value

Entry

K getKey()

V getValue()

V setValue(V value)

HashMap

HashMap

hash

Map

Hashtable

key-value

O(1)

HashMap

key

hashCode()

equals()

HashMap

key

hashCode()

equals()

hashCode()

equals()

hash

equals()

true

hashCode()

HashMap

Map

HashMap

equals()

true

hashCode()

hashCode()

hashCode()

equals()

true

hashCode()

equals()

hashCode()

hashCode()

int

hashcode

boolean

hashCode = (true ? 1 : 0);

float

hashCode = Float.floatToIntBits(f);

double

long value = Double.doubleToLongBits(f);

hashCode = (int)(value^(value>>>32));

int

short

byte

hashCode = (int)i;

long

hashCode = (int)(l^(l>>>32));

hashCode = object.hashCode();

hashcode

hashcode

hashcode

String

public int hashCode() {
int h = hash;
if (h == 0 && value.length > 0) {
char val[] = value;

for (int i = 0; i < value.length; i++) {
h = 31 * h + val[i];
}
hash = h;
}
return h;
}

String

hashCode()

Bean

/**
* @author jifang
* @since 16/1/13下午7:50.
*/
public class Bean implements Serializable {

private static final long serialVersionUID = 2975296536292876992L;

private boolean isUsed;

private double rate;

private String name;

@Override
public int hashCode() {
long rateHash = Double.doubleToLongBits(rate);
int isUsedHash = isUsed ? 1 : 0;
int nameHash = name.hashCode();

return nameHash * 11 + (int) (rateHash ^ (rateHash >>> 32)) * 13 + isUsedHash;
}

// ..

}

HashMap

/**
* Associates the specified value with the specified key in this map.
* If the map previously contained a mapping for the key, the old
* value is replaced.
*
* @param key key with which the specified value is to be associated
* @param value value to be associated with the specified key
* @return the previous value associated with <tt>key</tt>, or
*         <tt>null</tt> if there was no mapping for <tt>key</tt>.
*         (A <tt>null</tt> return can also indicate that the map
*         previously associated <tt>null</tt> with <tt>key</tt>.)
*/
public V put(K key, V value) {
if (table == EMPTY_TABLE) {
inflateTable(threshold);
}
if (key == null)
return putForNullKey(value);
int hash = hash(key);
int i = indexFor(hash, table.length);
for (Entry<K,V> e = table[i]; e != null; e = e.next) {
Object k;
if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
V oldValue = e.value;
e.value = value;
e.recordAccess(this);
return oldValue;
}
}

modCount++;
addEntry(hash, key, value, i);
return null;
}

/**
* Adds a new entry with the specified key, value and hash code to
* the specified bucket.  It is the responsibility of this
* method to resize the table if appropriate.
*
* Subclass overrides this to alter the behavior of put method.
*/
void addEntry(int hash, K key, V value, int bucketIndex) {
if ((size >= threshold) && (null != table[bucketIndex])) {
resize(2 * table.length);
hash = (null != key) ? hash(key) : 0;
bucketIndex = indexFor(hash, table.length);
}

createEntry(hash, key, value, bucketIndex);
}

/**
* Like addEntry except that this version is used when creating entries
* as part of Map construction or "pseudo-construction" (cloning,
* deserialization).  This version needn't worry about resizing the table.
*
* Subclass overrides this to alter the behavior of HashMap(Map),
* clone, and readObject.
*/
void createEntry(int hash, K key, V value, int bucketIndex) {
Entry<K,V> e = table[bucketIndex];
table[bucketIndex] = new Entry<>(hash, key, value, e);
size++;
}

Map

HashMap

TreeMap

HashSet

TreeSet

Map

key

key

key

key-value

Map

key

key

Set

value

Map

containsValue()

value

Map

public boolean containsValue(Object value) {
if (value == null)
return containsNullValue();

Entry[] tab = table;
for (int i = 0; i < tab.length ; i++)
for (Entry e = tab[i] ; e != null ; e = e.next)
if (value.equals(e.value))
return true;
return false;
}

/**
* Special-case code for containsValue with null argument
*/
private boolean containsNullValue() {
Entry[] tab = table;
for (int i = 0; i < tab.length ; i++)
for (Entry e = tab[i] ; e != null ; e = e.next)
if (e.value == null)
return true;
return false;
}

LinkedHashMap

LinkedHashMap

key-value

HashMap

Map

LinkedHashMap

addEntry()

HashMap

LinkedHashMap

put()

HashMap

LinkedHashMap

addEntry()

/**
* This override alters behavior of superclass put method. It causes newly
* allocated entry to get inserted at the end of the linked list and
* removes the eldest entry if appropriate.
*/
void addEntry(int hash, K key, V value, int bucketIndex) {
super.addEntry(hash, key, value, bucketIndex);

// Remove eldest entry if instructed
Entry<K,V> eldest = header.after;
if (removeEldestEntry(eldest)) {
removeEntryForKey(eldest.key);
}
}

/**
* This override differs from addEntry in that it doesn't resize the
* table or remove the eldest entry.
*/
void createEntry(int hash, K key, V value, int bucketIndex) {
HashMap.Entry<K,V> old = table[bucketIndex];
Entry<K,V> e = new Entry<>(hash, key, value, old);
table[bucketIndex] = e;
e.addBefore(header);
size++;
}

LinkedHashMap

/**
* @author jifang
* @since 16/1/28 上午10:33.
*/
public class MapClient {

private Random random = new Random();

@Test
public void clientLinkedHashMap() {
Map<String, Integer> map = new LinkedHashMap<>();
System.out.print("insert key:");
for (int i = 0; i < 20; ++i) {
String key = String.valueOf(random.nextInt(10));
System.out.printf(" %s", key);
if (map.get(key) == null) {
map.put(key, 1);
} else {
map.put(key, map.get(key) + 1);
}
}
System.out.printf("%n iterator:");

for (Map.Entry<String, Integer> entry : map.entrySet()) {
System.out.printf(" <%s -> %s>", entry.getKey(), entry.getValue());
}

}
}

WeakHashMap

WeakHashMap

HashMap

HashMap

key

HashMap

Map

key

WeakHashMap

key

key

WeakHashMap

key

key-value

@Test
public void clientWeakHashMap() {
Map<String, String> map = new WeakHashMap<>();
String key = "key";
map.put(key, "value");
map.put(new String("key1"), "value");
map.put(new String("key2"), "value");
System.out.printf("Before : %d%n", map.size());

System.gc();
System.runFinalization();
System.out.printf("After : %d ", map.size());
}

WeakHashMap

key

WeakHashMap

IdentityHashMap

HashMap

IdentityHashMap

==

equals()

public boolean containsKey(Object key) {
Object k = maskNull(key);
Object[] tab = table;
int len = tab.length;
int i = hash(k, len);
while (true) {
Object item = tab[i];
if (item == k)
return true;
if (item == null)
return false;
i = nextKeyIndex(i, len);
}
}

SortedMap-TreeMap

Map

SortedMap

key

key-value

TreeMap

SortedMap

key-value

TreeMap

key-value

key

TreeMap

SortedMap

Map

Comparator<? super K> comparator()

K    firstKey()

K    lastKey()

SortedMap<K,V>   headMap(K toKey)

SortedMap<K,V>   tailMap(K fromKey)

SortedMap<K,V>   subMap(K fromKey, K toKey)

TreeMap

SortedMap

Map.Entry<K,V>   ceilingEntry(K key)

K    ceilingKey(K key)

Map.Entry<K,V>   floorEntry(K key)

K    floorKey(K key)

Map.Entry<K,V>   higherEntry(K key)

K    higherKey(K key)

Map.Entry<K,V>   lowerEntry(K key)

K    lowerKey(K key)

Map.Entry<K,V>   pollFirstEntry()

Map.Entry<K,V>   pollLastEntry()

Map.Entry<K,V>    firstEntry()

Map.Entry<K,V>   lastEntry()

TreeMap

自然排序

TreeMap

key

Comparable

TreeMap

key

int compareTo(T o);

/**
* Compares two keys using the correct comparison method for this TreeMap.
*/
final int compare(Object k1, Object k2) {
return comparator==null ? ((Comparable<? super K>)k1).compareTo((K)k2)
: comparator.compare((K)k1, (K)k2);
}

java.lang.Comparable

int compareTo(T o);

String

Integer

public int compareTo(String anotherString) {
int len1 = value.length;
int len2 = anotherString.value.length;
int lim = Math.min(len1, len2);
char v1[] = value;
char v2[] = anotherString.value;

int k = 0;
while (k < lim) {
char c1 = v1[k];
char c2 = v2[k];
if (c1 != c2) {
return c1 - c2;
}
k++;
}
return len1 - len2;
}

HashMap

TreeMap

key

compareTo

public V get(Object key) {
Entry<K,V> p = getEntry(key);
return (p==null ? null : p.value);
}

final Entry<K,V> getEntry(Object key) {
// Offload comparator-based version for sake of performance
if (comparator != null)
return getEntryUsingComparator(key);
if (key == null)
throw new NullPointerException();
Comparable<? super K> k = (Comparable<? super K>) key;
Entry<K,V> p = root;
while (p != null) {
int cmp = k.compareTo(p.key);
if (cmp < 0)
p = p.left;
else if (cmp > 0)
p = p.right;
else
return p;
}
return null;
}

Comparable

/**
* @author jifang
* @since 16/1/13下午7:50.
*/
public class Bean implements Comparable<Bean> {

private boolean isUsed;

private double rate;

private String name;

public Bean(boolean isUsed, double rate, String name) {
this.isUsed = isUsed;
this.rate = rate;
this.name = name;
}

@Override
public int compareTo(Bean anotherBean) {
double another = (anotherBean.isUsed ? 1 : 0) +
anotherBean.rate + anotherBean.name.length();
double self = (isUsed ? 1 : 0) + rate + name.length();
return (int) (self - another);
}

@Override
public String toString() {
return "Bean{" +
"isUsed=" + isUsed +
", rate=" + rate +
", name='" + name + '\'' +
'}';
}
}

@Test
public void clientSortedMap() {
// value作为期望的order
SortedMap<Bean, Integer> map = new TreeMap<>();
map.put(new Bean(true, 3.14, "true"), 1);
// 该对象与上面的bean compare会返回0
map.put(new Bean(false, 3.14, "false"), 1);
map.put(new Bean(true, 3.14, "false"), 2);
map.put(new Bean(false, 3.14, "true"), 0);
System.out.println(map);

Bean firstKey = map.firstKey();
System.out.printf("first: %s -> %d%n", firstKey, map.get(firstKey));
Bean lastKey = map.lastKey();
System.out.printf("last: %s -> %d%n", lastKey, map.get(lastKey));

map.remove(firstKey);
Map.Entry<Bean, Integer> firstEntry = ((TreeMap<Bean, Integer>) map).firstEntry();
System.out.printf("A first: %s -> %d%n", firstEntry.getKey(), firstEntry.getValue());
}

remove

TreeMap

自定义排序

TreeMap

Comparator

key

Comparable

public class MapClient {

private Comparator<Bean> comparator = new Comparator<Bean>() {
@Override
public int compare(Bean o1, Bean o2) {
// 返回正数: 说明o1 > o2
// 返回负数: 说明o1 < o2
return -o1.compareTo(o2);
}
};

@Test
public void clientSortedMap() {
SortedMap<Bean, Integer> map = new TreeMap<>(comparator);
// ...
}
}

TreeMap

HashMap

O(1)

O(lgN)

key-value

key

EnumMap

EnumMap

Map

key

EnumMap

EnumMap

Map

EnumMap

key

key-value

EnumMap

key

null

null

value

/**
* @author jifang
* @since 16/1/27 下午4:01.
*/
public enum ShopListType {

BLACK_LIST(0, "黑名单"),
WHITE_LIST(1, "白名单"),
INVITE_LIST(2, "邀请名单"),
RECOMMEND_WHITE_LIST(3, "推荐白名单"),
RECOMMEND_BLACK_LIST(4, "推荐黑名单");

private int type;

private String description;

ShopListType(int type, String description) {
this.type = type;
this.description = description;
}

public int getValue() {
return type;
}

public String getDescription() {
return description;
}
}

@Test
public void clientEnumMap() {
EnumMap<ShopListType, String> map = new EnumMap<>(ShopListType.class);
map.put(ShopListType.BLACK_LIST, "黑名单");
map.put(ShopListType.WHITE_LIST, "白名单");
System.out.println(map);
}

Set

Set

Map

Map

key-value

Set

Map

Object

value

Set

private transient HashMap<E,Object> map;

// Dummy value to associate with an Object in the backing Map
private static final Object PRESENT = new Object();

public boolean add(E e) {
return map.put(e, PRESENT)==null;
}

Set

Collection

HashSet

HashSet

Set

Set

HashSet

HashMap

HashSet

null

LinkedHashSet

LinkedHashSet

LinkedHashMap

Set

LinkedHashSet

/**
* @author jifang
* @since 16/1/26 下午2:09.
*/
public class SetClient {

@Test
public void clientLinkedHashSet() {
Set<Integer> set = new LinkedHashSet<>();
for (int i = 0; i < 10; ++i) {
set.add(i);
}
for (int i = 19; i >= 10; --i) {
set.add(i);
}
System.out.println(set);
}
}

LinkedHashSet

LinkedHashMap

SortedSet-TreeSet

SortedSet

Set

SortedSet

TreeSet

SortedSet

Set

Comparator<? super E>    comparator()

E    first()

E    last()

SortedSet<E> tailSet(E fromElement)

SortedSet<E> headSet(E toElement)

SortedSet<E> subSet(E fromElement, E toElement)

TreeSet

SortedSet

E    ceiling(E e)

E    floor(E e)

Iterator<E>  descendingIterator()

NavigableSet<E>  descendingSet()

E    higher(E e)

E    lower(E e)

E    pollFirst()

E    pollLast()

TreeSet

TreeMap

TreeMap

EnumSet

EnumSet

Set

EnumSet

Enum

EnumSet

static

EnumSet

allOf(Class<E> elementType)

complementOf(EnumSet<E> s)

copyOf(Collection<E> c)

noneOf(Class<E> elementType)

of(E first, E... rest)

range(E from, E to)

@Test
public void clientEnumSet() {
EnumSet<ShopListType> set1 = EnumSet.allOf(ShopListType.class);
System.out.println(set1);

EnumSet<ShopListType> set2 = EnumSet.noneOf(ShopListType.class);
System.out.println(set2);
set2.add(ShopListType.BLACK_LIST);

System.out.println(set2);
}

EnumSet

EnumSet

Set

containsAll()

retainAll()

EnumSet

Collections

List

Map

Set

Collections

sort(List<T> list)

sort(List<T> list, Comparator<? super T> c)

shuffle(List<?> list)

swap(List<?> list, int i, int j)

reverse(List<?> list)

reverseOrder(Comparator<T> cmp)

rotate(List<?> list, int distance)

binarySearch(List<? extends Comparable<? super T>> list, T key)

binarySearch(List<? extends T> list, T key, Comparator<? super T> c)

indexOfSubList(List<?> source, List<?> target)

lastIndexOfSubList(List<?> source, List<?> target)

max(Collection<? extends T> coll)

max(Collection<? extends T> coll, Comparator<? super T> comp)

min(Collection<? extends T> coll)

min(Collection<? extends T> coll, Comparator<? super T> comp)

addAll(Collection<? super T> c, T... elements)

fill(List<? super T> list, T obj)

nCopies(int n, T o)

unmodifiableCollection(Collection<? extends T> c)

unmodifiableList(List<? extends T> list)

unmodifiableMap(Map<? extends K,? extends V> m)

unmodifiableSet(Set<? extends T> s)

unmodifiableSortedMap(SortedMap<K,? extends V> m)

unmodifiableSortedSet(SortedSet<T> s)

Set<T> singleton(T o)

singletonList(T o)

singletonMap(K key, V value)

emptyList()

emptyMap()

emptySet()

Collections

static List    EMPTY_LIST

static Map EMPTY_MAP

static Set EMPTY_SET

遗留的集合

Hashtable

Vactor

Stack

Enumeration

StringTokenizer

Enumeration

String

split()

hasMoreElements()

Properties

Properties

Hashtable

Map

Map

key-value

Map

String

Properties

key-value

String

Properties

key-value

String getProperty(String key)

String getProperty(String key, String defaultValue)

Object setProperty(String key, String value)

Enumeration<?>   propertyNames()

Set<String>  stringPropertyNames()

Properties

void list(PrintStream/PrintWriter out)

void load(InputStream/Reader in)

void store(OutputStream/Write out, String comments)

dubbo.version=1.0.0

## Data Source
mysql.driver.class=com.mysql.jdbc.Driver
mysql.url=jdbc:mysql://192.168.9.166:3306/common
mysql.user=admin
mysql.password=admin

@Test
public void clientProperties() throws IOException {
Properties properties = new Properties();
properties.load(ClassLoader.getSystemResourceAsStream("common.properties"));
System.out.println(properties.get("mysql.driver.class"));
properties.put("mysql.user", "root");
properties.put("mysql.password", "root");
properties.store(new FileOutputStream("common.properties"), "comment");
}

Properties

key-value

.properties