# User Defined Java Class
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Demonstration to illustrate the Modified JavaScript Value step. We're going to use: 'Replace' function to substitute characters in a string.
In this workshop, you will:
* Configure the following steps:
* User Defined Java Class
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User Defined Java Class
***
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{% tab title="Second Tab" %}
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{% tab title="1. Generate rows" %}
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{% tab title="2. UDJC" %}
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This Java code is part of a class or method that processes rows of data.
Let's break it down:
1. Import Statements:
```java
import java.util.*;
```
These statements import the `java.util` package, which includes various utility classes like `Calendar`.
2. Private Fields:
```java
private int yearIndex;
private Calendar calendar;
```
These are private instance fields of the class. `yearIndex` is an integer, and `calendar` is an instance of the `Calendar` class.
3. `processRow` Method: This method is used to process rows of data. It takes two parameters, `StepMetaInterface smi` and `StepDataInterface sdi`, and it may throw a `KettleException`.
* It checks if there is a row available for processing using `getRow()`. If there is no row, it marks the output as done and returns `false`.
* The `if (first)` block initializes some variables the first time this method is called. It finds the index of a field named "YEAR" in the input data, creates a `Calendar` instance, and clears it.
* It resizes the `outputRowData` array to match the output row's metadata size.
* It extracts the year value from the input row using `getInteger` and calculates the Easter date using the `easterDate` method.
* It adds the Easter date to the output row data and puts it into the output stream using `putRow`.
4. `easterDate` Method: This method calculates the date of Easter for a given year using the algorithm to determine the date of Easter Sunday.
* It takes the year as a parameter.
* It performs several mathematical calculations to determine the day, month, and year of Easter based on the input year.
* Finally, it sets the calculated date in the `calendar` instance and returns the `Date` object representing the Easter date.
Overall, this code is part of a data processing routine, and the `easterDate` method calculates the date of Easter for a given year using a well-known algorithm for determining Easter's date.
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