Essential Books

Increasing Decreasing calendar fields

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add() and roll() can be used to increase/decrease Calendar fields. 

Calendar calendar = new GregorianCalendar(2016, Calendar.MARCH, 31); // 31 March 2016

The add() method affects all fields, and behaves effectively if one were to add or subtract actual dates from the calendar 

calendar.add(Calendar.MONTH, -6);

The above operation removes six months from the calendar, taking us back to 30 September 2015.

To change a particular field without affecting the other fields, use roll(). 

calendar.roll(Calendar.MONTH, -6);

The above operation removes six months from the current month, so the month is identified as September. No other fields have been adjusted; the year has not changed with this operation.

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Calendar and its Subclasses:
* Calendar and its Subclasses
* Creating Calendar objects
* Increasing Decreasing calendar fields
* Finding AMPM
* Subtracting calendars
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0 Inheritance
1 Getting started with Java
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34 Calendar and its Subclasses
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121 SecurityManager
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124 java.util.Objects class
125 Java command: java and javaw
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129 sun.misc.Unsafe
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152 Generating Java Code
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156 Multi-release JAR files
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161 Using other scripting languages in Java
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176 Enum starting with a number
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180 StringBuffer
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182 C++ Comparison
183 CompletableFuture
184 Contributors