uk.ac.starlink.table.storage

Interface ColumnReader

public interface ColumnReader

Accessor for stored values. Although several data type accessor methods are provided, in general for a given instance of this interface not all of them will give a reasonable result; it is therefore the responsibility of the user of an instance of this class to keep track of what type is appropriate, since Java's type system will not enforce it. Attempting to retrieve the wrong type of data will give a result (it must not throw an exception), but this result may not be meaningful. This point of this non-type-safe arrangement is to make it possible to access primitive objects from this interface without the overhead of object creation.

Attempting to access a value with an index out of range for this reader will result in undefined behaviour.

Instances of this interface are not in general safe for concurrent access from different threads.

Since:

25 Apr 2017

Author:

Mark Taylor

Method Summary

Modifier and Type	Method and Description
boolean	getBooleanValue(long ix) Retrieve the current value of this sequence as a boolean value.
double	getDoubleValue(long ix) Retrieve the current value of this sequence as a floating point number.
int	getIntValue(long ix) Retrieve the current value of this sequence as an integer.
long	getLongValue(long ix) Retrieve the current value of this sequence as a long.
Object	getObjectValue(long ix) Retrieve the value at a given index as an object.
long	getRowCount() Returns the number of entries in this column.

Method Detail

getRowCount

long getRowCount()

Returns the number of entries in this column.

Returns:

row count

getObjectValue

Object getObjectValue(long ix)
               throws IOException

Retrieve the value at a given index as an object. Note it is permitted for the same instance to be returned each time, if the object is mutable it may have different values each time (for instance an array with different contents for each row). Therefore the state or contents of the returned object must not be relied on to stay the same between calls to this method.

Parameters:

ix - value index

Returns:

value

Throws:

IOException

getDoubleValue

double getDoubleValue(long ix)
               throws IOException

Retrieve the current value of this sequence as a floating point number.

Parameters:

ix - value index

Returns:

best-efforts floating point value

Throws:

IOException

getIntValue

int getIntValue(long ix)
         throws IOException

Retrieve the current value of this sequence as an integer.

Parameters:

ix - value index

Returns:

best-efforts integer value

Throws:

IOException

getLongValue

long getLongValue(long ix)
           throws IOException

Retrieve the current value of this sequence as a long.

Parameters:

ix - value index

Returns:

best-efforts long integer value

Throws:

IOException

getBooleanValue

boolean getBooleanValue(long ix)
                 throws IOException

Retrieve the current value of this sequence as a boolean value.

Parameters:

ix - value index

Returns:

best-efforts boolean value

Throws:

IOException