Category: java

file java

create text file from java with example

Post author By Rajesh Kumar
Post date March 3, 2020
No Comments on create text file from java with example

In this post, we are going to learn create text file from java with example

In this example, we are going to use File.java to create file

please make sure your code is under try catch block. Because there is chance to getting IOException

Prerequisites

Java installed
your program should have access to create file on the path

Syntax

	file.createNewFile();

Example

import java.io.File;

public class CreateFileExample {

	public static void main(String[] args) {
		try {
			File file = new File("C://temp//sample.txt");
			// .exists Method check if file already exists on the path
			if (!file.exists()) {
				// Below line will create file sample.txt on C://temp// folder
				file.createNewFile();
				System.out.println("File created succesfully !!");
			} else {

				System.err.println("File already exists");
			}

		} catch (Exception e) {
			e.printStackTrace();
		}
	}

}

Output

File created succesfully !!

if file already exists in the C://temp folder we will get below output

File already exists

Access denied

Make sure you have access from java to create file on the folder else you will get access denied exception like below

java.io.IOException: Access is denied
	at java.io.WinNTFileSystem.createFileExclusively(Native Method)
	at java.io.File.createNewFile(File.java:1012)
	at com.geeks.example.CreateFileEaxmple.main(CreateFileEaxmple.java:11)

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/files/CreateFileExample.java

how to read a file from java with example

Tags accessdenied, create, file, java

date java

calculate number days between two dates using java

Post author By Rajesh Kumar
Post date March 2, 2020
No Comments on calculate number days between two dates using java

In this tutorial, we will learn about calculate number days between two dates using java

There are lot of ways to calculate number of days between two dates in java

Using Java 8

In below example, we are going to use ChronoUnit to calculate days between two days

Syntax

ChronoUnit.DAYS.between(startDate, endDate);

Example


import java.time.LocalDate;
import java.time.Month;
import java.time.temporal.ChronoUnit;

public class CalculateDaysBetweenDatesJava8 {

	public static void main(String[] args) {
		try {
			// Start date is 2020-03-01 (YYYY-MM-dd)
			LocalDate startDate = LocalDate.of(2020, Month.MARCH, 1);

			// end date is 2020-03--03 (YYYY-MM-dd)
			LocalDate endDate = LocalDate.of(2020, Month.MARCH, 3);

			long numberOfDays = ChronoUnit.DAYS.between(startDate, endDate);

			System.out.println("Number of days " + numberOfDays);

		} catch (Exception e) {
			e.printStackTrace();
		}
	}

}

Output

Number of days 2

Above example is easiest way to calculate days between two dates

Int the below example we are going to use traditional way to calculate days between two days

Below Java 8

In below example we are going to use GregorianCalendar to calculate number of days between two dates

Example


import java.util.Calendar;
import java.util.GregorianCalendar;

public class CalculateDaysUsingCalender {

	public static void main(String[] args) {
		try {
			Calendar startDate = new GregorianCalendar();
			Calendar endDate = new GregorianCalendar();

			// Start date is 2020-03-01 (YYYY-MM-dd)
			startDate.set(2020, 03, 1);

			// end date is 2020-03--03 (YYYY-MM-dd)
			endDate.set(2020, 03, 3);

			// subtract emdTime-StartTime and divide by (1000 * 60 * 60 * 24)
			int i = (int) ((endDate.getTime().getTime() - startDate.getTime().getTime()) / (1000 * 60 * 60 * 24));
			System.out.println("Number of days " + i);

		} catch (Exception e) {
			e.printStackTrace();
		}
	}

}

Output

Number of days 2

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/CalculateDaysUsingCalender.java

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/CalculateDaysBetweenDatesJava8.java

convert String to date in java with example

compare two dates in java example

Tags calculate, date, java

java String

How to compare two strings in java

Post author By Rajesh Kumar
Post date February 27, 2020
No Comments on How to compare two strings in java

In this post, We will learn How to compare two strings in java

It might sounds easy. But we need to take care of few things while comparing two Strings

Avoid ==

If you are newbie to java, This might surprise you

while you use == to compare string it will not check the value of two strings

Instead of that it will check the reference of two Strings

"BeginnersBug" == new String("BeginnersBug") 
// Above check will return false

In the above snippet even though both the String are equal it will return false because both are not same object

.equals() method

.equlas method will compare two strings with the value irrespective of its object

Even though if it is two different object it will compare the value of two string

"BeginnersBug".equals(new String("BeginnersBug")) 
// Above check will return true

In the above code snippet it will compare two string value and it will return true for the condition

. equalsIgnoreCase() method

equalsIgnoreCase() method will ignore the case while checking the value of two Strings

If you want to check two Strings irrespective of case sensitive you can use this method

"beginnersbug".equalsIgnoreCase(new String("BeginnersBug")) 
// Above method will return true

In the above code snippet equalsIgnoreCase method will ignore the case sensitive. So it is returning true for the statement

Example


public class CompareStringExample {
	public static void main(String[] args) {
		try {
			// Example 1 == Below check will failS
			if ("BeginnersBug" == new String("BeginnersBug")) {
				System.out.println("Example 1 : Both the strings are equal");
			} else {
				System.out.println("Example 1 : Both the strings are not equal");
			}

			// Example 2 .equals()
			if ("BeginnersBug".equals(new String("BeginnersBug"))) {
				System.out.println("Example 2 : Both the strings are equal");
			} else {
				System.out.println("Example 2 : Both the strings are not equal");
			}

			// Example 3 .equalsIgnoreCase()
			if ("beginnersbug".equalsIgnoreCase(new String("BeginnersBug"))) {
				System.out.println("Example 3 : Both the strings are equal");
			} else {
				System.out.println("Example 3 : Both the strings are not equal");
			}

		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

Output

Example 1 : Both the strings are not equal
Example 2 : Both the strings are equal
Example 3 : Both the strings are equal

Reference

https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#equalsIgnoreCase(java.lang.String)

Convert String to lowercase using java

Print a String in java with example

Tags compare, java, string

collections java

get key and value from hashmap in java

Post author By Rajesh Kumar
Post date February 26, 2020
No Comments on get key and value from hashmap in java

In this tutorial, we will learn about get key and value from hashmap in java

Example Using Java 8


import java.util.HashMap;
import java.util.Map;

public class KeyValueFromHashMap {

	public static void main(String[] args) {
		try {
			Map<String, String> hashMap = new HashMap();
			hashMap.put("1", "Car");
			hashMap.put("2", "Bus");
			hashMap.put("3", "Train");

			// Below code only work above java 8
			hashMap.forEach((key, value) -> {
				System.out.println("Value of " + key + " is " + value);
			});

		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

Output

Value of 1 is Car
Value of 2 is Bus
Value of 3 is Train

Example using java 7


import java.util.HashMap;
import java.util.Map;

public class KeyValueFromHashMap {

	public static void main(String[] args) {
		try {
			Map<String, String> hashMap = new HashMap();
			hashMap.put("1", "Car");
			hashMap.put("2", "Bus");
			hashMap.put("3", "Train");

			for (Map.Entry<String, String> entry : hashMap.entrySet()) {
				System.out.println(entry.getKey() + " Value is " + entry.getValue());
			}

		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

Output

1 Value is Car
2 Value is Bus
3 Value is Train

GitHub Url

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/KeyValueFromHashMap.java

Check key exists in Hashmap Java

Tags hashmap, java8, key, vaue

collections java

iterate stream with index in Java8

Post author By Rajesh Kumar
Post date February 25, 2020
No Comments on iterate stream with index in Java8

In this post, we will learn to iterate stream with index in Java8

We will come across multiple streams tutorials, but in all the tutorials we never iterate with index numbers

In order to find the current index or other numeric operations index number will help us to get the position

In this tutorial, we are going to use IntStream to get index of the arraylist

Because there is no straight way to get index number in streams

Syntax

IntStream.range(start, end)

Example


import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;

public class IterateStreamWithIndex {

	public static void main(String[] args) {
		try {
			List<String> list = new ArrayList<String>();
			list.add("India");
			list.add("USA");
			list.add("Germany");

			IntStream.range(0, list.size())
					.forEach(x -> System.out.println("The index is " + x + " Value is " + list.get(x)));

		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

Output

The index is 0 Value is India
The index is 1 Value is USA
The index is 2 Value is Germany

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/IterateStreamWithIndex.java

foreach in java8 using streams

sorting operations in java using streams

Tags iterate, java8, streams

java

convert int to String in java with example

Post author By Rajesh Kumar
Post date February 22, 2020
No Comments on convert int to String in java with example

In this post, we will learn to convert int to String in java with example

Even this is a simple post, But it is difficult to remember all syntax. We can easily convert int to String using valueOf() method

Syntax

String.valueOf(i);

Example

public class ConvertInttoString {

	public static void main(String[] args) {

		int i = 99;
		String stringValue = String.valueOf(i);
		System.out.println("Converted String " + stringValue);
	}

}

Output

Converted String 99

Convert String to lowercase using java

convert String to date in java with example

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/ConvertInttoString.java

Tags int to string, java, string

collections java

foreach in java8 using streams

Post author By Rajesh Kumar
Post date February 22, 2020
No Comments on foreach in java8 using streams

In this tutorial, we will learn about foreach in java8 using streams

In java8, We can easily iterate a list using streams.

Streams API provided a lot of features. In this post, we are going to see about foreach

Syntax

stream().forEach({operations});

Example


import java.util.ArrayList;
import java.util.List;

public class ForEachExample {

	public static void main(String[] args) {
		try {

			List studentList = new ArrayList();
			Student student = null;

			student = new Student();
			student.setId(1);
			student.setName("Rajesh");
			student.setAddress("Mumbai");
			studentList.add(student);

			student = new Student();
			student.setId(1);
			student.setName("Kumar");
			student.setAddress("Chennai");
			studentList.add(student);

			studentList.stream()
					.forEach(x -> System.out.println("Name is " + x.getName() + " Address is " + x.getAddress()));

		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

Student.java


public class Student {

	private int id;
	private String name;
	private String address;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}

}

Output

Name is Rajesh Address is Mumbai
Name is Kumar Address is Chennai

sorting operations in java using streams

Iterate list using streams in java

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/ForEachExampleUsingStreams.java

Tags arraylist, foreach, java, java8, streams

date java

compare two dates in java example

Post author By Rajesh Kumar
Post date February 20, 2020
No Comments on compare two dates in java example

In this post, we will learn to compare two dates in java example

There are multiple ways to compare two dates in java.

In the First example we will learn to compare dates using compareTo() method

While using compareTo() method we are having 3 chances of output. Below are the possible output

0 – When both the dates are equal

1 – When date 1 is greater than date 2

-1 – When date 1 is lesser than date 2

Syntax

date1.compareTo(date2)

Example


import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateCompareExample {
	public static void main(String[] args) {
		try {

			String date1 = "22/02/2020";
			String date2 = "21/02/2020";
			DateFormat format = new SimpleDateFormat("DD/MM/yyyy");
			Date dateObj1 = format.parse(date1);
			Date dateObj2 = format.parse(date2);

			// If Both the date are same comparTo Method will return 0
			if (dateObj1.compareTo(dateObj2) == 0) {
				System.out.println("Both the dates are Equal !!");
			} // If date1 greater than date 2 it will return 1
			else if (dateObj1.compareTo(dateObj2) > 0) {

				System.out.println("Date 1 is greater than date 2");
			} // If date1 lesser than date 2 it will return -1
			else {
				System.out.println("Date 1 is lesser than date 2");
			}

		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

Date 1 is greater than date 2

Using equals(),after(),before()

In the above example, we learned using compareTo() method. But we can compare dates using predefined functions also.

Below example is another way to compare two dates in java

equals() – return true if both the dates are equal

after() – return true if date 1 greater than date 2

before() – return true if date 1 lesser than date 2

Example


import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateCompareExample {
	public static void main(String[] args) {
		try {

			String date1 = "20/02/2020";
			String date2 = "21/02/2020";
			DateFormat format = new SimpleDateFormat("DD/MM/yyyy");
			Date dateObj1 = format.parse(date1);
			Date dateObj2 = format.parse(date2);

			// If Both the date are same comparTo Method will return 0
			if (dateObj1.equals(dateObj2)) {
				System.out.println("Both the dates are Equal !!");
			} // If date1 greater than date 2 it will return 1
			else if (dateObj1.after(dateObj2)) {

				System.out.println("Date 1 is after than date 2");
			} // If date1 lesser than date 2 it will return -1
			else if (dateObj1.before(dateObj2)) {
				System.out.println("Date 1 is before than date 2");
			}

		} catch (Exception e) {
			e.printStackTrace();
		}

	}

}

Output

Date 1 is before than date 2

Reference

https://docs.oracle.com/javase/8/docs/api/java/util/Date.html#compareTo-java.util.Date-

convert String to date in java with example

Tags compare, date, java

date java

convert String to date in java with example

Post author By Rajesh Kumar
Post date February 20, 2020
No Comments on convert String to date in java with example

In this tutorial, we will learn to convert String to date in java with example.While we working with java this is one of the most scenario

We can easily convert String to Data using SimpleDateFormat.java. But before that we should know the date patterns which mentioned below

Letter	Component	Presentation	Examples
y	Year	Year	1996; 96
M	Month in year	Month	July; Jul; 07
d	Day in month	Number	10
a	Am/pm marker	Text	PM
H	Hour in day (0-23)	Number	0
k	Hour in day (1-24)	Number	24
K	Hour in am/pm (0-11)	Number	0
h	Hour in am/pm (1-12)	Number	12
m	Minute in hour	Number	30
s	Second in minute	Number	55
S	Millisecond	Number	978

In this example we will convert 20/02/2020 to Date class

Syntax

DateFormat simpleDateFormat = new SimpleDateFormat("dd/MM/YYYY");
 simpleDateFormat.parse(dateString);

Example


import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class SimpleDateFormatExample {

	public static void main(String[] args) {
		try {
			String dateString = "20/02/2020";
			DateFormat simpleDateFormat = new SimpleDateFormat("dd/MM/YYYY");
			// Below line will convert from string to date
			Date parse = simpleDateFormat.parse(dateString);
			// The output will be like Sun Dec 29 00:00:00 IST 2019
			System.out.println(" Output :: "+parse);
		} catch (ParseException e) {
			e.printStackTrace();
		}

	}

}

Output

 Output :: Sun Dec 29 00:00:00 IST 2019

Reference

https://docs.oracle.com/javase/8/docs/api/java/text/SimpleDateFormat.html

Download

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/SimpleDateFormatExample.java

print current date in java with example

compare two dates in java example

Tags date, java

date java

add 3 days to the current date in java

Post author By Rajesh Kumar
Post date February 18, 2020
1 Comment on add 3 days to the current date in java

In this post we will learn to add 3 days to the current date in java
While we working with dates we will come up with adding or subtracting from the current date

In Java there are lot of method for Date. So it is little bit difficult to remember all the things.

In this example we used Calendar.java and Date.java from java.util package
In below example we added 3 days

Syntax

object.add(Calendar.DAY_OF_YEAR, 1)

Example

import java.util.Calendar;
import java.util.Date;

public class AddDaysToDate {

	public static void main(String[] args) {
		try {
			Calendar calender = Calendar.getInstance();
			Date beforeAdding = calender.getTime();
			System.out.println("Printing the value before adding date ::: " + beforeAdding);

			// Adding the 3 days below
			calender.add(Calendar.DAY_OF_YEAR, 3);
			Date afterAdding = calender.getTime();
			System.out.println("Printing the value after adding date  ::: " + afterAdding);

		} catch (Exception e) {
			e.printStackTrace();
		}
	}

}

Output

Printing the value before adding date ::: Thu Feb 13 17:00:21 IST 2020
Printing the value after adding date  ::: Sun Feb 16 17:00:21 IST 2020

Github

https://github.com/rkumar9090/BeginnersBug/blob/master/BegineersBug/src/com/geeks/example/AddDaysToDate.java

convert String to date in java with example

compare two dates in java example

Tags date, java

Prerequisites

Syntax

Example

Output

Access denied

Github

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Using Java 8

Syntax

Example

Output

Below Java 8

Example

Output

Github

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Avoid ==

.equals() method

. equalsIgnoreCase() method

Example

Output

Reference

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Example Using Java 8

Output

Example using java 7

Output

GitHub Url

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Syntax

Example

Output

Github

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Example

Output

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Syntax

Example

Student.java

Output

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Github

Syntax

Example

Using equals(),after(),before()

Example

Output

Reference

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Example

Output

Reference

Download

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Example

Output

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