edu.cmu.cs.cs214.hw5.core

Class DataResult

java.lang.Object

edu.cmu.cs.cs214.hw5.core.DataResult

public final class DataResult
extends java.lang.Object

A DataResult represents the result of attempting to load data from a data source. Such an attempt may result in either failure or success. If the result is failure, the plugin must provide a detailed failure message by calling the failure(String) method. Otherwise, the plugin should provide a list of the columns retrieved from the data source by calling the success(List) method.

The success or failure of a result can be determined via the isSuccess() method, and the relevant fields can be extracted via result() and error(). If the “wrong”method is called—for example, if the result was actually failure but you call result()—then the method will raise a NoSuchElementException.

Method Summary

Modifier and Type	Method and Description
java.lang.String	error() Get the error message associated with this result, asserting that it failed.
static DataResult	failure(java.lang.String error) Create a result that indicates that the data retrieval failed to complete because of the given reason.
boolean	isSuccess() Determine whether this represents a successful computation.
java.util.List<Column>	result() Get the list of columns associated with this result, asserting that it is successful.
static DataResult	success(java.util.List<Column> columns) Create a result that indicates that the data retrieval completed successfully and returned the provided list of columns.

Methods inherited from class java.lang.Object

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

Method Detail

success

public static DataResult success(java.util.List<Column> columns)

Create a result that indicates that the data retrieval completed successfully and returned the provided list of columns.

Parameters:

columns - the list of columns containing the data that was retrieved

Returns:

a new DataResult to represent the result of the successful computation

Throws:

java.lang.NullPointerException - if columns == null

failure

public static DataResult failure(java.lang.String error)

Create a result that indicates that the data retrieval failed to complete because of the given reason. The provided message should be human-readable, and should provide all the information required for the user to correct the error.

Parameters:

error - a detailed message describing the source of the error

Returns:

a new DataResult to represent the result of the failed computation

Throws:

java.lang.NullPointerException - if error == null

isSuccess

public boolean isSuccess()

Determine whether this represents a successful computation. If this object was created via success(List), the method will return true; if it was created via failure(String), the method will return false.

Returns:

true if this represents a successful computation, or false if it represents a failed computation

result

public java.util.List<Column> result()
                              throws java.util.NoSuchElementException

Get the list of columns associated with this result, asserting that it is successful. Only use this method if you can prove that the result was successful, likely due to an immediately preceding call to isSuccess().

Returns:

the list of columns containing the data that was retrieved

Throws:

java.util.NoSuchElementException - if this computation was not successful

See Also:

isSuccess()

error

public java.lang.String error()
                       throws java.util.NoSuchElementException

Get the error message associated with this result, asserting that it failed. Only use this method if you can prove that the result was a failure, likely due to an immediately preceding call to isSuccess().

Returns:

the error message associated with this computation

Throws:

java.util.NoSuchElementException - if this computation was successful

See Also:

isSuccess()