类 MapUtils

方法详细资料

• newHashMap

  public static <K,V> HashMap<K,V> newHashMap()

  Creates a mutable, empty HashMap instance.

  Note: if mutability is not required, use ImmutableMap.of() instead.

  Note: if K is an enum type, use newEnumMap instead.

  Note for Java 7 and later: this method is now unnecessary and should be treated as deprecated. Instead, use the HashMap constructor directly, taking advantage of the new "diamond" syntax.

  返回:

  a new, empty HashMap

• newTreeMap

  public static <K extends Comparable,V> TreeMap<K,V> newTreeMap()

  Creates a mutable, empty TreeMap instance using the natural ordering of its elements.

  Note: if mutability is not required, use ImmutableSortedMap.of() instead.

  Note for Java 7 and later: this method is now unnecessary and should be treated as deprecated. Instead, use the TreeMap constructor directly, taking advantage of the new "diamond" syntax.

  返回:

  a new, empty TreeMap

• newHashMapWithExpectedSize

  public static <K,V> HashMap<K,V> newHashMapWithExpectedSize(int expectedSize)

  Creates a HashMap instance, with a high enough "initial capacity" that it should hold expectedSize elements without growth. This behavior cannot be broadly guaranteed, but it is observed to be true for OpenJDK 1.7. It also can't be guaranteed that the method isn't inadvertently oversizing the returned map.

  参数:

  expectedSize - the number of entries you expect to add to the returned map

  返回:

  a new, empty HashMap with enough capacity to hold expectedSize entries without resizing

  抛出:

  IllegalArgumentException - if expectedSize is negative

• newLinkedHashMap

  public static <K,V> LinkedHashMap<K,V> newLinkedHashMap()

  Creates a mutable, empty, insertion-ordered LinkedHashMap instance.

  Note: if mutability is not required, use ImmutableMap.of() instead.

  Note for Java 7 and later: this method is now unnecessary and should be treated as deprecated. Instead, use the LinkedHashMap constructor directly, taking advantage of the new "diamond" syntax.

  返回:

  a new, empty LinkedHashMap

• newLinkedHashMapWithExpectedSize

  public static <K,V> LinkedHashMap<K,V> newLinkedHashMapWithExpectedSize(int expectedSize)

  Creates a LinkedHashMap instance, with a high enough "initial capacity" that it should hold expectedSize elements without growth. This behavior cannot be broadly guaranteed, but it is observed to be true for OpenJDK 1.7. It also can't be guaranteed that the method isn't inadvertently oversizing the returned map.

  参数:

  expectedSize - the number of entries you expect to add to the returned map

  返回:

  a new, empty LinkedHashMap with enough capacity to hold expectedSize entries without resizing

  抛出:

  IllegalArgumentException - if expectedSize is negative

  从以下版本开始:

  19.0