KeySelector (FoundationDB Java Client API)

java.lang.Object
- com.foundationdb.KeySelector

```
public class KeySelector
extends Object
```
A KeySelector identifies a particular key in the database. FoundationDB's lexicographically ordered data model permits finding keys based on their order (for example, finding the first key in the database greater than a given key). Key selectors represent a description of a key in the database that could be resolved to an actual key by Transaction's getKey() or used directly as the beginning or end of a range in Transaction's getRange().

For more about how key selectors work in practice, see the KeySelector documentation.

Generally one of the following static methods should be used to construct a KeySelector:
This is an immutable class. The add(int) call does not modify internal state, but returns a new instance.

Constructor Summary

Constructors
Constructor and Description

KeySelector(byte[] key, boolean orEqual, int offset)
Constructs a new KeySelector from the given parameters.

Constructors
Constructor and Description
`KeySelector(byte[] key, boolean orEqual, int offset)` Constructs a new `KeySelector` from the given parameters.

Method Summary

Methods
Modifier and Type	Method and Description
`KeySelector`	`add(int offset)` Returns a new `KeySelector` offset by a given number of keys from this one.
`static KeySelector`	`firstGreaterOrEqual(byte[] key)` Creates a `KeySelector` that picks the first key greater than or equal to the parameter
`static KeySelector`	`firstGreaterThan(byte[] key)` Creates a `KeySelector` that picks the first key greater than the parameter
`byte[]`	`getKey()` Returns a copy of the key that serves as the anchor for this `KeySelector`.
`int`	`getOffset()` Returns the key offset for this `KeySelector`.
`static KeySelector`	`lastLessOrEqual(byte[] key)` Creates a `KeySelector` that picks the last key less than or equal to the parameter
`static KeySelector`	`lastLessThan(byte[] key)` Creates a `KeySelector` that picks the last key less than the parameter
`String`	`toString()`

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - KeySelector
```
public KeySelector(byte[] key,
           boolean orEqual,
           int offset)
```
    Constructs a new KeySelector from the given parameters. Client code will not generally call this constructor.
    
    Parameters:
    key - the base key to reference
    orEqual - true if the key should be considered for equality
    offset - the number of keys to offset from once the key is found
- Method Detail
  - lastLessThan
```
public static KeySelector lastLessThan(byte[] key)
```
    Creates a KeySelector that picks the last key less than the parameter
    
    Parameters:
    key - the key to use as the edge of the edge of selection criteria
    
    Returns:
    a newly created KeySelector
  - lastLessOrEqual
```
public static KeySelector lastLessOrEqual(byte[] key)
```
    Creates a KeySelector that picks the last key less than or equal to the parameter
    
    Parameters:
    key - the key to use as the edge of the edge of selection criteria
    
    Returns:
    a newly created KeySelector
  - firstGreaterThan
```
public static KeySelector firstGreaterThan(byte[] key)
```
    Creates a KeySelector that picks the first key greater than the parameter
    
    Parameters:
    key - the key to use as the edge of the edge of selection criteria
    
    Returns:
    a newly created KeySelector
  - firstGreaterOrEqual
```
public static KeySelector firstGreaterOrEqual(byte[] key)
```
    Creates a KeySelector that picks the first key greater than or equal to the parameter
    
    Parameters:
    key - the key to use as the edge of the edge of selection criteria
    
    Returns:
    a newly created KeySelector
  - add
```
public KeySelector add(int offset)
```
    Returns a new KeySelector offset by a given number of keys from this one. For example, an offset of 1 means that the new KeySelector specifies the key in the database after the key selected by this KeySelector. The offset can be negative; these will move the selector to previous keys in the database.
    
    Note that large offsets take time O(offset) to resolve, making them a poor choice for iterating through a large range. (Instead, use the keys returned from a range query operation themselves to create a new beginning KeySelector.) For more information see the KeySelector documentation.
    
    Parameters:
    offset - the number of keys to offset the KeySelector. This number can be negative.
    
    Returns:
    a newly created KeySelector that is offset by a number of keys.
  - getKey
```
public byte[] getKey()
```
    Returns a copy of the key that serves as the anchor for this KeySelector. This is not the key to which this KeySelector would resolve to. For this function see ReadTransaction.getKey(KeySelector).
    
    Returns:
    a copy of the "anchor" key for this KeySelector.
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - getOffset
```
public int getOffset()
```
    Returns the key offset for this KeySelector. For internal use.

Class KeySelector

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

KeySelector

Method Detail

lastLessThan

lastLessOrEqual

firstGreaterThan

firstGreaterOrEqual

add

getKey

toString

getOffset