tech.tablesaw.columns

Class ColumnReference

java.lang.Object

tech.tablesaw.columns.ColumnReference

Direct Known Subclasses:

BooleanColumnReference, DateColumnReference, DateTimeColumnReference, NumberColumnReference, StringColumnReference, TimeColumnReference

public class ColumnReference
extends Object

A reference to a column that can be used in evaluating query predicates. It is a key part of having a fluent API for querying tables.

Basically, it lets you write a query like this:

table.select(column("foo").isEqualTo("Bar"));

In that example, column() is a static method that returns a ColumnReference for a column named "foo". The method isEqualTo(), is implemented on ColumnReference in a way that it can be applied to potentially, multiple column types, although in this case, it only makes sense for CategoryColumns since the argument is a string.

When select() isExecuted, it supplies the table to the ColumnReference. The ColumnReference uses the table and columnName to get access to the right column, and then fulfils its role by ensuring that the filtering "isEqualTo("Bar") is applied to all the cells in the column.

Constructor Summary

Constructors

Constructor and Description
ColumnReference(String column)

Method Summary

Modifier and Type	Method and Description
String	getColumnName()
Filter	isMissing()
Filter	isNotMissing()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ColumnReference

public ColumnReference(String column)

Method Detail

getColumnName

public String getColumnName()

isNotMissing

public Filter isNotMissing()

isMissing

public Filter isMissing()