Package com.exonum.binding.core.storage.indices

Interface EntryIndex<T>

Type Parameters:

T - the type of an element in this entry

All Superinterfaces:

StorageIndex

All Known Subinterfaces:

ProofEntryIndex<T>

All Known Implementing Classes:

EntryIndexProxy, ProofEntryIndexProxy

public interface EntryIndex<T>
extends StorageIndex

An Entry is a database index that may or may not contain a single value.

An Entry is analogous to Optional, but provides modifying ("destructive") operations when created with a Fork. Such methods are specified to throw UnsupportedOperationException if the entry is created with a Snapshot — a read-only database access.

All method arguments are non-null by default.

When the access goes out of scope, this entry is destroyed. Subsequent use of the closed entry is prohibited and will result in IllegalStateException.

See Also:

Access

Method Summary

Modifier and Type	Method	Description
T	get()	If value is present in the entry, returns it, otherwise, throws NoSuchElementException.
boolean	isPresent()	Returns true if this entry exists in the database.
T	orElse(T valueIfAbsent)	Returns the value of this entry, if it is present; otherwise, the given value.
void	remove()	Removes a value from this entry.
void	set(T value)	Sets a new value of the entry, overwriting the previous value.
Optional<T>	toOptional()	Converts the entry to Optional.

Methods inherited from interface com.exonum.binding.core.storage.indices.StorageIndex

getAddress, getName

Method Detail

set

void set(T value)

Sets a new value of the entry, overwriting the previous value.

Parameters:

value - a value to set. Must not be null.

Throws:

UnsupportedOperationException - if the entry is read-only

IllegalStateException - if the index is invalid

isPresent

boolean isPresent()

Returns true if this entry exists in the database.

Throws:

IllegalStateException - if the index is invalid.

get

T get()

If value is present in the entry, returns it, otherwise, throws NoSuchElementException.

Throws:

NoSuchElementException - if a value is not present in the Entry

IllegalStateException - if the index is invalid

IllegalArgumentException - if the supplied serializer cannot decode the value

orElse

T orElse(T valueIfAbsent)

Returns the value of this entry, if it is present; otherwise, the given value.

Parameters:

valueIfAbsent - a value to return if there is none in this entry

Throws:

IllegalStateException - if the index is invalid

IllegalArgumentException - if the supplied serializer cannot decode the value

remove

void remove()

Removes a value from this entry.

Throws:

UnsupportedOperationException - if the entry is read-only.

IllegalStateException - if the index is invalid

toOptional

Optional<T> toOptional()

Converts the entry to Optional.

Be aware that this method represents a state of the entry at the time of calling. And the returned value won't reflect the entry changes:

  
    entry.set("foo");
    Optional<String> optionalEntry = entry.toOptional();
    entry.remove();
    optionalEntry.get(); // -> returns "foo"
  
 

Returns:

Optional.of(value) if value is present in the entry, otherwise returns Optional.empty()