How to read a file in java with example program

We can read java file using buffered reader class in java

We need to import java.io.BufferedReader in order to read java text file.

Create object of java.io.BufferedReader class by passing new FileReader("C:\\Sample.txt") object to the constructor.

In order to read line by line call readLine() method of BufferedReader class which returns current line. Initially first line of java text file

 Program #1: Write a java program to read a file line by line using BufferedReader class 

package com.instanceofjava.javareadfile;

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

public class ReadFileBufferedReader {

 /**

  * 

  * @category: How to read java read file line by line using buffered reader

  */

public static void main(String[] args) {

  BufferedReader breader = null;

 try {

 String CurrentLine;

 breader = new BufferedReader(new FileReader("E://Sample.txt"));

 while ((CurrentLine = breader.readLine()) != null) {

    System.out.println(CurrentLine);

 }

} catch (IOException e) {

   e.printStackTrace();

} finally {

    try {

 if (breader != null)

     breader.close();

     } catch (IOException ex) {

    ex.printStackTrace();

     }

}

}

}

 Output:

  

Java open and read file

Read file line by line in java

Example java program to read a file line by line

java read file line by line example

Java example program to print message without using System.out.println()

Is it possible to print message without using system.out.println?




Yes its possible to print message without using System.out.println("");

System.out.write("www.corejavawithselenium.blogspot.in\n".getBytes());
 System.out.format("%s", "www.java.com \n")
 PrintStream myout =  new PrintStream(new FileOutputStream(FileDescriptor.out));
   myout.print("www.corejavawithselenium.blogspot.in \n");
System.err.print("This is custom error message");
System.console().writer().println("Hai");

1.System.out.write(Byte [] arg0);

System.out.write(Byte [] arg0) method The java.io.FilterOutputStream.write(byte[] b) method writes b.length bytes to this output stream.

package com.instanceofjava;

public class PrintMessage {

public static void main(String[] args) throws IOException{

       System.out.write("Hello World".getBytes());
}
}

Output:

Hello World

2. PrintStream  java.io.PrintStream.format(String arg0, Object... arg1)

System.out.format("format",Object obj) by using this method we can format the text and print

package com.instanceofjava;

public class PrintMessage {

public static void main(String[] args){

        System.out.format("%s", "James");
}

}

Output:

James

3. FileDescriptor:

Create PrintStream object by passing FileOutputStream(FileDescriptor.out) object as an argument to the constructor
package com.instanceofjava;

public class PrintMessage {

public static void main(String[] args){

       PrintStream myout =  new PrintStream(new FileOutputStream(FileDescriptor.out));
          myout.print("i love Java");
}
}

Output:

i love java


4. System.err.print(""):

We can use System.err.print("") method to print the message actually its used to print error message
package com.instanceofjava;

public static void main(String[] args){

       System.err.print("This is custom error message");
}
}

Output:

This is custom error message


5.System.console().writer().println("");

System.console() returns null if your application is not run in a terminal System.console() provides methods for reading password without echoing characters

package com.instanceofjava;

public static void main(String[] args){

       System.err.print("This is custom error message");
}
}

Output:

This is custom error message Exception in thread "main" java.lang.NullPointerException
    at PrintMessage.main(PrintMessage.java:24)

How to open notepad using java program

Notepad is a text editor from windows operating system. We use notepad for writing text files.

We can open a new notepad using java code.

By using the concept of running another application by Runtime class in java.

By creating object of runtime and calling  exec() method by passing application name.

Lets see how to open a notepad using java code

OutPut::

Program #1: Java example program to open notepad

1. package interestingJavaprograms;
2. import java.io.IOException;
3.  
4. public class NotepadJava {
5.  
6.     /**
7.      * @ www.corejavawithselenium.blogspot.in
8.      * @ how to open a new notepad using java program
9.      */
10. public static void main(String[] args) {
11.        
12.           Runtime rt = Runtime.getRuntime();
13.           
14. try {
15.       rt.exec("notepad");
16. }
17.  catch (IOException ex) {
18.  
19.  System.out.println(ex);
20.  
21. }  
22.  
23. }
24.  
25. }

OUPUT::

How to sort arraylist of strings alphabetically java

1.Basic Java example program to sort arraylist of strings

1. package com.javasortarraylistofobjects;
2.  
3. import java.util.ArrayList;
4. import java.util.Collections;
5. import java.util.Iterator;
6.  
7. public class SortArrayList{
8.  
9. public static void main(String[] args) {
10.   
11. //create an ArrayList object
12. ArrayList<String> arrayList = new ArrayList();
13.        
14. //Add elements to Arraylist
15.         
16. arrayList.add("A"); 
17. arrayList.add("C");
18. arrayList.add("D");
19. arrayList.add("Z");
20. arrayList.add("F");
21. arrayList.add("J");
22. arrayList.add("K");
23. arrayList.add("M");
24. arrayList.add("L");
25. arrayList.add("O");
26.        
27.         
28.  System.out.println("Before sorting ArrayList ...");
29.  Iterator itr=arrayList.iterator();
30.         
31. while (itr.hasNext()) {
32.  
33. System.out.println(itr.next());
34.      
35. }
36.  
37.        
38.  /*
39.  To sort an ArrayList object, use Collection.sort method. This is a
40.   static method. It sorts an ArrayList object's elements into ascending order.
41. */
42.   Collections.sort(arrayList);
43.      
44.   System.out.println("After sorting ArrayList ...");
45.        
46.     
47.         
48. Iterator itr1=arrayList.iterator();
49.         
50. while (itr1.hasNext()) {
51. 
    
52. System.out.println(itr1.next());
53.             
54. }
55.     
56.   
57. }
58. }

OUTPUT::

1. Before sorting ArrayList ...
2. A
3. C
4. D
5. Z
6. F
7. J
8. K
9. M
10. L
11. O
12. After sorting ArrayList ...
13. A
14. C
15. D
16. F
17. J
18. K
19. L
20. M
21. O
22. Z

How to find largest element in an array with index and value using array

How to find largest element in an array with index and value using array?

package com.inofjava;
public class Array {

public static void main(String[] args) {

int arr[]={1,120,56,78,87};
int largest=arr[0];
int smallest=arr[0];
int small=0;
int index=0;

for(int i=1;i<arr.length;i++){

if(arr[i]>largest){

largest=arr[i];
index=i;

}
else if(smallest>arr[i]){

smallest=arr[i];
small=i;

}
}

System.out.println(largest);
System.out.println(index);
System.out.println(smallest);
System.out.println(small);

}

}


Output:
120
1
87
4

Encapsulation in java with example program

What is meant by encapsulation in java? 

• Binding the data with its related functionalities known as encapsulation
• Here data means variables and functionalities means methods.
• So keeping the variable and related methods in one place.
• That place is "class". class is the base for encapsulation.
• Lets see example program on encapsulation, how the variables and methods defined in a class

What is encapsulation in object oriented programming?

Basic java example program on data encapsulation:

1. package com.java;
2.  
3. public class EncapsulationDemo {
4.  
5.   String name;
6.   int rno;
7.   String address;
8.  
9. public String getName() {
10.        return name;
11.  }
12.  
13. public void setName(String name) {
14.         this.name = name;
15. } 
16. 
    
17. public int getRno() {
18.        return rno;
19. }
20.  
21. public void setRno(int rno) {
22.      this.rno = rno;
23. }
24.  
25. public String getAddress() {
26.         return address;
27. }
28.  
29.  public void setAddress(String address) {
30.     this.address = address;
31. }
32.  
33. public void showInfo(){
34.  
35.       System.out.println("Name: "+getName());
36.       System.out.println("R.No: "+getRno());
37.       System.out.println("Name: "+getAddress());
38.  
39.     }
40. }

Class:

The above example program shows how the variables and methods will be there in a class.

So class is the base for encapsulation

class is user defined data type in java means by using class we can structure our own programs.

Lest see a example program on class.

1. package com.java;
2.  
3. public class ClassDemo {
4.  
5.     //variables of a class
6.    String empName;
7.    int empId;
8.    String Designation;
9.  
10.  //getter and setter methods for variables 
11.  //by using these methods we can set the value to the variable and gat the value from the
12.  //variables
13.  
14.  public String getEmpName() {
15.         return empName;
16. }
17.  
18.  public void setEmpName(String empName) {
19.       this.empName = empName;
20. }
21.  
22. public int getEmpId() {
23.        return empId;
24. }
25.  
26. public void setEmpId(int empId) {
27.         this.empId = empId;
28. }
29. 
    
30. public String getDesignation() {
31.         return Designation;
32. }
33.  
34.  public void setDesignation(String designation) {
35.         Designation = designation;
36. }
37. 
    
38. }

Object:

Instance of class is known as object.

Instance means dynamic memory allocation. So dynamic memory allocation to class is called object.

By using "new" keyword the object will be created dynamically.

Class is a template. By using object we will get memory for all variables so that we can use them.

We can create number of objects for one class based on our requirements.

Below an example program on class and object.

1. package com.java; 
2.  
3. public class User {
4.  
5.    String Name;
6.     int Id;
7.     String address;
8.  
9.  public String getName() {
10.      return Name;
11. }
12.  
13. public void setName(String name) {
14.         Name = name;
15. }
16.  
17. public int getId() {
18.       return Id;
19. }
20.  
21. public void setId(int id) {
22.        Id = id;
23. }
24.  
25. public String getAddress() {
26.         return address;
27. }
28.  
29. public void setAddress(String address) {
30.         this.address = address;
31. }
32.  
33. public static void main(String [] args){
34.  
35.        User obj= new User();
36.  
37.         obj.setName("sai");
38.         obj.setId(1);
39.         obj.setAddress("xyz");
40.  
41.         System.out.println(obj.getName());
42.         System.out.println(obj.getId());
43.         System.out.println(obj.getAddress());
44.  
45.     }
46. }

Output:

1. sai
2. 1
3. xyz