HashMap | Notion

Modifier and Type	Method and Description
`void`	[`clear](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#clear-->)()`Removes all of the mappings from this map.
`Object`	[`clone](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#clone-->)()`Returns a shallow copy of this HashMap instance: the keys and values themselves are not cloned.
`V`	[compute](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#compute-K-java.util.function.BiFunction->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [BiFunction](<https://docs.oracle.com/javase/8/docs/api/java/util/function/BiFunction.html>)<? super [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> remappingFunction)Attempts to compute a mapping for the specified key and its current mapped value (or `null` if there is no current mapping).
`V`	[`computeIfAbsent](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#computeIfAbsent-K-java.util.function.Function->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [Function](<https://docs.oracle.com/javase/8/docs/api/java/util/function/Function.html>)<? super [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> mappingFunction)`If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null`.
`V`	[computeIfPresent](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#computeIfPresent-K-java.util.function.BiFunction->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [BiFunction](<https://docs.oracle.com/javase/8/docs/api/java/util/function/BiFunction.html>)<? super [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> remappingFunction)If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.
`boolean`	[`containsKey](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#containsKey-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) key)`Returns true if this map contains a mapping for the specified key.
`boolean`	[`containsValue](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#containsValue-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) value)`Returns true if this map maps one or more keys to the specified value.
[`Set](<https://docs.oracle.com/javase/8/docs/api/java/util/Set.html>)<[Map.Entry](<https://docs.oracle.com/javase/8/docs/api/java/util/Map.Entry.html>)<[K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),[V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)>>`	[`entrySet](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#entrySet-->)()`Returns a `Set` view of the mappings contained in this map.
`void`	[`forEach](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#forEach-java.util.function.BiConsumer->)([BiConsumer](<https://docs.oracle.com/javase/8/docs/api/java/util/function/BiConsumer.html>)<? super [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> action)`Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
`V`	[`get](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#get-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) key)`Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
`V`	[`getOrDefault](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#getOrDefault-java.lang.Object-V->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) defaultValue)`Returns the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key.
`boolean`	[`isEmpty](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#isEmpty-->)()`Returns true if this map contains no key-value mappings.
[`Set](<https://docs.oracle.com/javase/8/docs/api/java/util/Set.html>)<[K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)>`	[`keySet](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#keySet-->)()`Returns a `Set` view of the keys contained in this map.
`V`	[merge](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#merge-K-V-java.util.function.BiFunction->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) value, [BiFunction](<https://docs.oracle.com/javase/8/docs/api/java/util/function/BiFunction.html>)<? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> remappingFunction)If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value.
`V`	[`put](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#put-K-V->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) value)`Associates the specified value with the specified key in this map.
`void`	[`putAll](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#putAll-java.util.Map->)([Map](<https://docs.oracle.com/javase/8/docs/api/java/util/Map.html>)<? extends [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> m)`Copies all of the mappings from the specified map to this map.
`V`	[`putIfAbsent](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#putIfAbsent-K-V->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) value)`If the specified key is not already associated with a value (or is mapped to `null`) associates it with the given value and returns `null`, else returns the current value.
`V`	[`remove](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#remove-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) key)`Removes the mapping for the specified key from this map if present.
`boolean`	[`remove](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#remove-java.lang.Object-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) key, [Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) value)`Removes the entry for the specified key only if it is currently mapped to the specified value.
`V`	[`replace](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#replace-K-V->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) value)`Replaces the entry for the specified key only if it is currently mapped to some value.
`boolean`	[`replace](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#replace-K-V-V->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) oldValue, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) newValue)`Replaces the entry for the specified key only if currently mapped to the specified value.
`void`	[`replaceAll](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#replaceAll-java.util.function.BiFunction->)([BiFunction](<https://docs.oracle.com/javase/8/docs/api/java/util/function/BiFunction.html>)<? super [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> function)`Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception.
`int`	[`size](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#size-->)()`Returns the number of key-value mappings in this map.
[`Collection](<https://docs.oracle.com/javase/8/docs/api/java/util/Collection.html>)<[V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)>`	[`values](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#values-->)()`Returns a `Collection` view of the values contained in this map.

Modifier and Type	Method and Description
`void`	[`clear](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#clear-->)()`Removes all of the mappings from this map.
`Object`	[`clone](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#clone-->)()`Returns a shallow copy of this HashMap instance: the keys and values themselves are not cloned.
`V`	[compute](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#compute-K-java.util.function.BiFunction->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [BiFunction](<https://docs.oracle.com/javase/8/docs/api/java/util/function/BiFunction.html>)<? super [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> remappingFunction)Attempts to compute a mapping for the specified key and its current mapped value (or `null` if there is no current mapping).
`V`	[`computeIfAbsent](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#computeIfAbsent-K-java.util.function.Function->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [Function](<https://docs.oracle.com/javase/8/docs/api/java/util/function/Function.html>)<? super [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> mappingFunction)`If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null`.
`V`	[computeIfPresent](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#computeIfPresent-K-java.util.function.BiFunction->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [BiFunction](<https://docs.oracle.com/javase/8/docs/api/java/util/function/BiFunction.html>)<? super [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> remappingFunction)If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.
`boolean`	[`containsKey](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#containsKey-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) key)`Returns true if this map contains a mapping for the specified key.
`boolean`	[`containsValue](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#containsValue-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) value)`Returns true if this map maps one or more keys to the specified value.
[`Set](<https://docs.oracle.com/javase/8/docs/api/java/util/Set.html>)<[Map.Entry](<https://docs.oracle.com/javase/8/docs/api/java/util/Map.Entry.html>)<[K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),[V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)>>`	[`entrySet](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#entrySet-->)()`Returns a `Set` view of the mappings contained in this map.
`void`	[`forEach](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#forEach-java.util.function.BiConsumer->)([BiConsumer](<https://docs.oracle.com/javase/8/docs/api/java/util/function/BiConsumer.html>)<? super [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> action)`Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
`V`	[`get](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#get-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) key)`Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
`V`	[`getOrDefault](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#getOrDefault-java.lang.Object-V->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) defaultValue)`Returns the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key.
`boolean`	[`isEmpty](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#isEmpty-->)()`Returns true if this map contains no key-value mappings.
[`Set](<https://docs.oracle.com/javase/8/docs/api/java/util/Set.html>)<[K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)>`	[`keySet](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#keySet-->)()`Returns a `Set` view of the keys contained in this map.
`V`	[merge](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#merge-K-V-java.util.function.BiFunction->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) value, [BiFunction](<https://docs.oracle.com/javase/8/docs/api/java/util/function/BiFunction.html>)<? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> remappingFunction)If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value.
`V`	[`put](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#put-K-V->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) value)`Associates the specified value with the specified key in this map.
`void`	[`putAll](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#putAll-java.util.Map->)([Map](<https://docs.oracle.com/javase/8/docs/api/java/util/Map.html>)<? extends [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> m)`Copies all of the mappings from the specified map to this map.
`V`	[`putIfAbsent](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#putIfAbsent-K-V->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) value)`If the specified key is not already associated with a value (or is mapped to `null`) associates it with the given value and returns `null`, else returns the current value.
`V`	[`remove](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#remove-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) key)`Removes the mapping for the specified key from this map if present.
`boolean`	[`remove](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#remove-java.lang.Object-java.lang.Object->)([Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) key, [Object](<https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html>) value)`Removes the entry for the specified key only if it is currently mapped to the specified value.
`V`	[`replace](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#replace-K-V->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) value)`Replaces the entry for the specified key only if it is currently mapped to some value.
`boolean`	[`replace](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#replace-K-V-V->)([K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) key, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) oldValue, [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>) newValue)`Replaces the entry for the specified key only if currently mapped to the specified value.
`void`	[`replaceAll](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#replaceAll-java.util.function.BiFunction->)([BiFunction](<https://docs.oracle.com/javase/8/docs/api/java/util/function/BiFunction.html>)<? super [K](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? super [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>),? extends [V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)> function)`Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception.
`int`	[`size](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#size-->)()`Returns the number of key-value mappings in this map.
[`Collection](<https://docs.oracle.com/javase/8/docs/api/java/util/Collection.html>)<[V](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html>)>`	[`values](<https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#values-->)()`Returns a `Collection` view of the values contained in this map.