Simple Way to Import all Missing Packages at Once : Eclipse shortcut

Posted by: Instanceofjava Posted date: March 13, 2016 / comment : 0

1.How to import all missing packages at once in java program eclipse:

  • While writing a java program or copied some line to eclipse then we need to import corresponding java packages.
  • Instead of checking one by one there is a short cut in eclipse to import corresponding packages at once
  • There is a short cut key to import all missing packages at once
  • "CTL+SHIFT+O" then one popup will come with all corresponding packages so we need to select corresponding missing package name then it automatically come. one by one it will automatically ask and we need to select.
  • Lets see an example program.

1.Copy This program and paste in eclipse and remove all packages.
2.Then it will show some errors on classes 
3. select CTL+SHIFT+O
4.Select missing packages


  1. package com.javacheckvaluehashmap;
  2.  
  3.  
  4. public class HashmapExample{
  5.  
  6. public static void main(String[] args) {
  7.   
  8. //create an Hashmap object
  9. HashMap<String, String> hashmap = new HashMap();
  10.        
  11. //Add key values pairs to hashmap
  12.         
  13. hashmap.put("1","One");
  14. hashmap.put("2","Two");
  15. hashmap.put("3","Three");
  16. hashmap.put("4","Four");
  17. hashmap.put("5","Five");
  18. hashmap.put("6","Six");       
  19.         
  20.        
  21. boolean isExists = hashmap.containsValue("Six");
  22. System.out.println("The value Six exists in HashMap ? : " + isExists);
  23.     
  24.  
  25. if(!hashmap.isEmpty()){
  26.  
  27. Iterator it=hashmap.entrySet().iterator();
  28.              
  29. while(it.hasNext()){

  31. Map.Entry obj=(Entry) it.next();
  32. System.out.print(obj.getKey()+" ");
  33. System.out.println(obj.getValue());
  34.              
  35. }           
  36. }   
  37.  
  38. }
  39.  
  40. }
     


eclipse short cut import all missing packages at once





import all missing packages once java program



Java Basic example program to check particular value exists in hashmap

Posted by: Instanceofjava Posted date: March 13, 2016 / comment : 0 ,

1.Basic Java example program to check particular value exists in hashmap


  1. package com.javacheckvaluehashmap;
  2.  
  3. import java.util.Hashmap;
  4. import java.util.Iterator;
  5. import java.util.Map;
  6. import java.util.Map.Entry;
  7.  
  8. public class HashmapExample{
  9.  
  10. public static void main(String[] args) {
  11.   
  12. //create an Hashmap object
  13. HashMap<String, String> hashmap = new HashMap();
  14.        
  15. //Add key values pairs to hashmap
  16.         
  17. hashmap.put("1","One");
  18. hashmap.put("2","Two");
  19. hashmap.put("3","Three");
  20. hashmap.put("4","Four");
  21. hashmap.put("5","Five");
  22. hashmap.put("6","Six");       
  23.         
  24.  
  25.  /*
  26.  To check whether a particular value exists in HashMap use
  27.  boolean containsValue(Object value) method of HashMap class.
  28. containsValue(Object value) returns true if the HashMap contains mapping for specified
  29. value otherwise false.*/
  30.        
  31. boolean isExists = hashmap.containsValue("Six");
  32. System.out.println("The value Six exists in HashMap ? : " + isExists);
  33.     
  34.  
  35. if(!hashmap.isEmpty()){
  36.  
  37. Iterator it=hashmap.entrySet().iterator();
  38.              
  39. while(it.hasNext()){

  41. Map.Entry obj=(Entry) it.next();
  42. System.out.print(obj.getKey()+" ");
  43. System.out.println(obj.getValue());
  44.              
  45. }           
  46. }   
  47.  
  48. }
  49.  
  50. }
     



Output:

  1. The value Six exists in HashMap ? : true
  2. 1 One
  3. 2 Two
  4. 3 Three
  5. 4 Four
  6. 5 Five
  7. 6 Six

check particular value exits in hashmap

Basic Java Example program Check if a particular key exists HashMap

Posted by: Instanceofjava Posted date: March 13, 2016 / comment : 0 ,

1.Basic Java example program to check particular key exists in hashmap

  1. package com.javacheckkeyhashmap;
  2.  
  3. import java.util.Hashmap;
  4. import java.util.Iterator;
  5. import java.util.Map;
  6. import java.util.Map.Entry;
  7.  
  8. public class HashmapExample{
  9.  
  10. public static void main(String[] args) {
  11.   
  12. //create an Hashmap object
  13. HashMap<String, String> hashmap = new HashMap();
  14.        
  15. //Add key values pairs to hashmap
  16.         
  17. hashmap.put("1","One");
  18. hashmap.put("2","Two");
  19. hashmap.put("3","Three");
  20. hashmap.put("4","Four");
  21. hashmap.put("5","Five");
  22. hashmap.put("6","Six");       
  23.         
  24.  
  25.  /*
  26.   To check whether a particular key exists in HashMap use
  27.    boolean containsKey(Object key) method of HashMap class.
  28.   containsKey(Object key) returns true if the HashMap contains mapping for specified key
  29.   otherwise false.
  30.  */
  31.  
  32. boolean isExists = hashmap.containsKey("4");
  33. System.out.println("4 exists in HashMap ? : " + isExists);
  34.     
  35.  
  36. if(!hashmap.isEmpty()){
  37.  
  38. Iterator it=hashmap.entrySet().iterator();
  39.              
  40. while(it.hasNext()){

  42. Map.Entry obj=(Entry) it.next();
  43. System.out.print(obj.getKey()+" ");
  44. System.out.println(obj.getValue());
  45.              
  46. }           
  47. }   
  48.  
  49. }
  50.  
  51. }
     



Output:

  1. 4 exists in HashMap ? : true
  2. 1 One
  3. 2 Two
  4. 3 Three
  5. 4 Four
  6. 5 Five
  7. 6 Six

Six different ways to iterate list in java

Posted by: Instanceofjava Posted date: March 11, 2016 / comment : 1

How many ways we can iterate list in java?

  • We can iterate list in 6  different ways in java.
  1. For Loop
  2. Enhanced For Loop
  3. While Loop
  4. Iterator
  5. Collections stream() util (Java8 feature)
  6. ListIterator

different ways to iterate list in java


1. Iterate list using For loop


1.Basic Java example program to iterate arraylist elements using list iterator
  1. package com.javaIteratelist;
  2.  
  3. import java.util.ArrayList;
  4. import java.util.Collections;
  5. import java.util.Iterator;
  6.  
  7. public class IterateList{
  8.  
  9. public static void main(String[] args) {
  10.   
  11. //create an ArrayList object
  12.  List<String> instanceofjavaList = new ArrayList<String>();
  13.        
  14. //Add elements to Arraylist
  15.  
  16. // add 5 different values to arraylist 
  17. instanceofjavaList.add("Interview Questions");
  18. instanceofjavaList.add("Interview Programs");
  19. instanceofjavaList.add("Concept and example program");
  20. instanceofjavaList.add("Concept and interview questions");
  21. instanceofjavaList.add("Java Quiz");
  22.     
  23. for (int i = 0; i < instanceofjavaList.size(); i++) {
  24.  
  25.     System.out.println(instanceofjavaList.get(i));
  26.  
  27. }

  29. }
  30.  
  31. }
     



Output:

  1. Interview Questions
  2. Interview Programs
  3. Concept and example program
  4. Concept and interview questions
  5. Java Quiz


 2. Iterate list using Enhanced For loop

  1. package com.javaIteratelist;
  2.  
  3. import java.util.ArrayList;
  4. import java.util.Iterator;
  5.  
  6. public class IterateList{
  7.  
  8. public static void main(String[] args) {
  9.   
  10. //create an ArrayList object
  11. List<String> instanceofjavaList = new ArrayList<String>();
  12.        
  13. //Add elements to Arraylist
  14.  
  15. // add 5 different values to arraylist 
  16. instanceofjavaList.add("Interview Questions");
  17. instanceofjavaList.add("Interview Programs");
  18. instanceofjavaList.add("Concept and example program");
  19. instanceofjavaList.add("Concept and interview questions");
  20. instanceofjavaList.add("Java Quiz");
  21.  
  22. for (String str: instanceofjavaList) {
  23.             System.out.println(str);
  24. }

  26. }
  27.  
  28. }
     


Output:

  1. Interview Questions
  2. Interview Programs
  3. Concept and example program
  4. Concept and interview questions
  5. Java Quiz


 3. Iterate list using while loop

  1. package com.javaIteratelist;
  2.  
  3. import java.util.ArrayList;
  4. import java.util.Iterator;
  5.  
  6. public class IterateList{
  7.  
  8. public static void main(String[] args) {
  9.   
  10. //create an ArrayList object
  11. List<String> instanceofjavaList = new ArrayList<String>();
  12.        
  13. //Add elements to Arraylist
  14.  
  15. // add 5 different values to arraylist 
  16. instanceofjavaList.add("Interview Questions");
  17. instanceofjavaList.add("Interview Programs");
  18. instanceofjavaList.add("Concept and example program");
  19. instanceofjavaList.add("Concept and interview questions");
  20. instanceofjavaList.add("Java Quiz");
  21.  
  22.  
  23. int i = 0;
  24.  
  25. while (i < instanceofjavaList.size()) {
  26.  
  27.   System.out.println(instanceofjavaList.get(i));
  28.   i++;
  29. }

  31. }
  32.  
  33. }
     


Output:

  1. Interview Questions
  2. Interview Programs
  3. Concept and example program
  4. Concept and interview questions
  5. Java Quiz

 4. Iterate list using iterator

  1. package com.javaIteratelist;
  2.  
  3. import java.util.ArrayList;
  4. import java.util.Iterator;
  5.  
  6. public class IterateList{
  7.  
  8. public static void main(String[] args) {
  9.   
  10. //create an ArrayList object
  11. List<String> instanceofjavaList = new ArrayList<String>();
  12.        
  13. //Add elements to Arraylist
  14.  
  15. // add 5 different values to arraylist 
  16. instanceofjavaList.add("Interview Questions");
  17. instanceofjavaList.add("Interview Programs");
  18. instanceofjavaList.add("Concept and example program");
  19. instanceofjavaList.add("Concept and interview questions");
  20. instanceofjavaList.add("Java Quiz");
  21.  
  22.  
  23. Iterator<String> itr = instanceofjavaList.iterator();
  24.  
  25. while (itr.hasNext()) {
  26.      System.out.println(itr.next());
  27. }
  28.  
  29. }
  30.  
  31. }
     


Output:

  1. Interview Questions
  2. Interview Programs
  3. Concept and example program
  4. Concept and interview questions
  5. Java Quiz


 5. Iterate list using Stream API.

  1. package com.javaIteratelist;
  2.  
  3. import java.util.ArrayList;
  4. public class IterateList{
  5.  
  6. public static void main(String[] args) {
  7.   
  8. //create an ArrayList object
  9. List<String> instanceofjavaList = new ArrayList<String>();
  10.        
  11. //Add elements to Arraylist
  12.  
  13. // add 5 different values to arraylist 
  14. instanceofjavaList.add("Interview Questions");
  15. instanceofjavaList.add("Interview Programs");
  16. instanceofjavaList.add("Concept and example program");
  17. instanceofjavaList.add("Concept and interview questions");
  18. instanceofjavaList.add("Java Quiz");
  19.  
  20.  
  21. instanceofjavaList.forEach((name) -> {
  22.             System.out.println(name);
  23.         }); 

  25. }
  26.  
  27. }
     


Output:

  1. Interview Questions
  2. Interview Programs
  3. Concept and example program
  4. Concept and interview questions
  5. Java Quiz

6. Using List erator:

You Might Like:

1.What are all the different places to create object in java

Java program to insert an element to ArrayList using ListIterator Example

Posted by: Instanceofjava Posted date: March 11, 2016 / comment : 1 , ,

1.Basic Java example program to insert element using list iterator to arraylist
  1. package com.javaIteratearraylistiterator;
  2.  
  3. import java.util.ArrayList;
  4. import java.util.Collections;
  5. import java.util.Iterator;
  6.  
  7. public class IterateListIteratorArrayList{
  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("B");
  18. arrayList.add("C");
  19. arrayList.add("D");
  20. arrayList.add("F");
  21. arrayList.add("F");
  22. arrayList.add("G");
  23. arrayList.add("H");
  24. arrayList.add("I");
  25.     
  26.         
  27.  /*
  28. Get a ListIterator object for ArrayList using
  29. istIterator() method.
  30. */
  31.   
  32. System.out.println("Before inserting element");
  33.  
  34. for(int intIndex = 0; intIndex < arrayList.size(); intIndex++)
  35.               System.out.println(arrayList.get(intIndex)); 
  36. ListIterator itr = arrayList.listIterator();
  37.        
  38. /*
  39.       Use void add(Object o) method of ListIterator to add or insert an element
  40.       to List. It adds an element just before the element that would have
  41.       been returned by next method call and after the element that would have
  42.       returned by previous call.
  43.     */
  44.    
  45.     itr .next();
  46.        
  47.     //Add an element
  48.     itr .add("Added Element");
  49.     /*
  50.  
  51. System.out.println("After inserting element .");
  52.  
  53. for(int intIndex = 0; intIndex < arrayList.size(); intIndex++)
  54.               System.out.println(arrayList.get(intIndex));   
  55.  
  56. }
  57. }
     



Output:

  1. Before inserting element
  2. A
  3. B
  4. C
  5. D
  6. F
  7. F
  8. G
  9. H
  10. I
  11. After inserting element .
  12. A
  13. Added Element
  14. B
  15. C
  16. D
  17. F
  18. F
  19. G
  20. H
  21. I

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

Posted by: Instanceofjava Posted date: March 10, 2016 / comment : 0

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


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

  1. System.out.write("www.instanceofjava.com \n".getBytes());
  2.  System.out.format("%s", "www.instanceofjava.com \n")
  3.  PrintStream myout =  new PrintStream(new FileOutputStream(FileDescriptor.out));
       myout.print("www.instanceofjava.com \n");
  4. System.err.print("This is custom error message");
  5. System.console().writer().println("Hai");

print without system.out.println()



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.

  1. package com.instanceofjava;
  2.  
  3. public class PrintMessage {

  5. public static void main(String[] args) throws IOException{
  6.  
  7.        System.out.write("Hello World".getBytes());
  8. }
  9. }

Output:

  1. 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

  1. package com.instanceofjava;
  2.  
  3. public class PrintMessage {

  5. public static void main(String[] args){
  6.  
  7.         System.out.format("%s", "James");
  8. }
  9.  
  10. }

Output:

  1. James

3. FileDescriptor:

  • Create PrintStream object by passing FileOutputStream(FileDescriptor.out) object as an argument to the constructor
  1. package com.instanceofjava;
  2.  
  3. public class PrintMessage {

  5. public static void main(String[] args){
  6.  
  7.        PrintStream myout =  new PrintStream(new FileOutputStream(FileDescriptor.out));
              myout.print("i love Java");
  8. }
  9. }

Output:

  1. 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
  1. package com.instanceofjava;
  2.  
  3. public static void main(String[] args){
  4.  
  5.        System.err.print("This is custom error message");
  6. }
  7. }

Output:

  1. 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

  1. package com.instanceofjava;
  2.  
  3. public static void main(String[] args){
  4.  
  5.        System.err.print("This is custom error message");
  6. }
  7. }

Output:

  1. This is custom error messageException in thread "main" java.lang.NullPointerException
        at PrintMessage.main(PrintMessage.java:24)
Subscribe to: Posts ( Atom )
Select Menu
Copyright © 2015-2025 instanceofjava.com , All rights reserved | Privacy policy | About Us