LocalDate and LocalDateTime

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Java 8 LocalDate and LocalDateTime objects

Date and LocalDate objects cannot be exactly converted between each other since a Date object represents both a specific day and time, while a LocalDate object does not contain time or timezone information. However, it can be useful to convert between the two if you only care about the actual date information and not the time information.

Creates a LocalDate

// Create a default date
LocalDate lDate = LocalDate.now();
 
// Creates a date from values
lDate = LocalDate.of(2014, 10, 13);
 
// create a date from string
lDate = LocalDate.parse("2014-12-18");
 
// creates a date from zone
LocalDate.now(ZoneId.systemDefault());
 

Creates a LocalDateTime

// Create a default date time
LocalDateTime lDateTime = LocalDateTime.now();
 
// Creates a date time from values
lDateTime = LocalDateTime.of(2018, 10, 18, 11, 30);
 
// create a date time from string
lDateTime = LocalDateTime.parse("2018-10-05T11:30:30");
 
// create a date time from zone
LocalDateTime.now(ZoneId.systemDefault());

LocalDate to Date and vice-versa

Date date = Date.from(Instant.now());
ZoneId defaultZoneId = ZoneId.systemDefault();
 
// Date to LocalDate
LocalDate localDate = date.toInstant().atZone(defaultZoneId).toLocalDate();
 
// LocalDate to Date
Date.from(localDate.atStartOfDay(defaultZoneId).toInstant());

LocalDateTime to Date and vice-versa

Date date = Date.from(Instant.now());
ZoneId defaultZoneId = ZoneId.systemDefault();
 
// Date to LocalDateTime
LocalDateTime localDateTime = date.toInstant().atZone(defaultZoneId).toLocalDateTime();
 
// LocalDateTime to Date
Date out = Date.from(localDateTime.atZone(defaultZoneId).toInstant());

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LocalTime

To use just the time part of a Date use LocalTime. You can instantiate a LocalTime object in a couple ways

1. LocalTime time = LocalTime.now();
2. time = LocalTime.MIDNIGHT;
3. time = LocalTime.NOON;
4. time = LocalTime.of(12, 12, 45);

LocalTime also has a built in toString method that displays the format very nicely.

System.out.println(time);

you can also get, add and subtract hours, minutes, seconds, and nanoseconds from the LocalTime object i.e.

time.plusMinutes(1);
time.getMinutes();
time.minusMinutes(1);

You can turn it into a Date object with the following code:

LocalTime lTime = LocalTime.now();
Instant instant = lTime.atDate(LocalDate.of(A_YEAR, A_MONTH, A_DAY)).
      atZone(ZoneId.systemDefault()).toInstant();
Date time = Date.from(instant);

this class works very nicely within a timer class to simulate an alarm clock.

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Basic Programs

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• Creating Your First Java Program
• Type Conversion
• Getters and Setters
• Reference Data Types
• Java Compiler - javac
• Documenting Java Code
• Command line Argument Processing
• Java Command - java and javaw
• Literals
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Strings in Java

• Comparing Strings
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• Finding a String Within Another String
• String pool and heap storage
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• Remove Whitespace from the Beginning and End of a String and Case insensitive switch
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• Counting occurrences of a substring or character in a string

StringBuffer and StringBuilder

• String Buffer
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Date Class

• Convert java.util.Date to java.sql.Date and Basic date
• LocalDate and LocalDateTime objects
• Creating a Specific Date and Converting Date to String format
• Convert formatted string representation of date to Date object
• Comparing Date objects
• Converting String into Date and Time Zones and java.util.Date

Dates and Time (java.time.*)

• Dates and Time
• Date Time Formatting and Date Manipulations
• LocalTime

BigDecimal

• Comparing and Using BigDecimals
• BigDecimal.valueOf()
• Mathematical operations with BigDecimal

BigInteger

• Initialization and Generating random BigIntegers
• BigInteger Mathematical Operations Examples
• NumberFormat

Bit Manipulation

• Checking, setting, clearing, and toggling individual bits. Using long as bit mask
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Arrays

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• Removing items from a List within a loop
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Sets

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• Declaring and using a basic enum
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super keyword

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Calendar and its Subclasses

• Creating, Subtracting and Finding AM/PM Calendar

Using the static keyword

• Reference to non-static member from static context

Properties Class

• Reference to non-static member from static context

Lambda Expressions

• Introduction to Java lambdas
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Basic Control Structures

• Switch, do while, For Each, Continue Statement in Java
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BufferedWriter

• Write a line of text to File

New File I/O

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• Migrating from java.io.File to Java 7 NIO
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Scanner

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Interfaces

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Regular Expressions

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Comparable and Comparator

• Sorting a List using Comparable<T> or a Comparator<T>
• compareTo, compare Methods and Natural vs explicit sorting

Java Floating Point Operations

• Comparing floating point values
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Currency and Money

• Add custom currency

Object Cloning

• Cloning performing a deep copy and copy factory
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Recursion

• Basic idea of Recursion
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• Computing the Nth Fibonacci Number and power of a number

Converting to and from Strings

• Converting String to other datatypes
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Random Number Generation

• Pseudo Random Numbers in Specific Range
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Singletons

• Enum Singleton and Singleton without use of Enum, Thread safe Singleton
• Extending singleton (singleton inheritance)

Autoboxing

• Using int and Integer interchangeably and Auto-unboxing may lead to NullPointerException
• Different Cases When Integer and int can be used interchangeably

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