How to convert Alphanumeric to Numeric String

 

Hi.

have you faced scenarios like you have alphanumeric String and you have requirement to use numeric String to fullfil your requirement, like if need to convert in other data type later.

so here is Magic in below programe:- 

package com.neesri.sorting;

public class AlphanumericToNumeric {

public static void main(String[] args) {

// convert alphanumeric string into numeric string

String str = "a12334tyz78x";

str = str.replaceAll("[^\\d]", "");

System.out.println("Alphanumeric string to Number "+ str);

}

}

======output====

Alphanumeric string to Number 1233478

Happy Learning :) 

How many ways can convert HashMap to List

Hi,

Today we will talk about how we can convert Hashmap into ArrayList.

1. we have converted keys of HashMap into List.

2. we have converted all values of Map into List.

3. we have converted all entries(key  & values) of HashMap into List.

In below i have explained programme stepwise:- 

package com.neesri.sorting;   import java.util.ArrayList; import java.util.Collection; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map.Entry; import java.util.Set;   public class ConvertMapToList {      // we can convert Hashmap into Arraylist through three ways      public static void main(String[] args) {              HashMap<String, Integer> hashmapObj = new HashMap<>();            hashmapObj.put("Zimbabwe", 600);            hashmapObj.put("India", 700);            hashmapObj.put("SriLanka", 400);            hashmapObj.put("Nepal", 800);              // 1-----convert Hashmap Key into List            // using keyset method retun set view            Set<String> setViewOfMapKeys = hashmapObj.keySet();            // convert set into list            List<String> listObj = new ArrayList<>(setViewOfMapKeys);              System.out.println("Hashmap Keys into list------>");            for (String printList : listObj) {                 System.out.println(printList);            }              // 2. Convert Hashmap Values into List              Collection<Integer> values = hashmapObj.values();            List<Integer> list = new ArrayList<>(values);            System.out.println("Hashmap values into List----->");            for (Integer hashmapValuesIntoList : list) {                 System.out.println(hashmapValuesIntoList);            }              // 3. Convert hashmap all entries into List              Set<Entry<String, Integer>> entriesObjSet = hashmapObj.entrySet();            List<Entry<String, Integer>> listEntries = new ArrayList<>(entriesObjSet);              // System.out.println("Hashmap all entries into List======>");            /*             * for(Object obj:listEntries) {             *             * System.out.println(obj); }             */            // OR              /*             * for(Entry<String, Integer> obj:listEntries) {             *             * System.out.println(obj); }             */              // OR            System.out.println("Printing thorough iterator======>");            Iterator<Entry<String, Integer>> iterator = listEntries.iterator();              while (iterator.hasNext()) {                 Entry<String, Integer> entry = iterator.next();                   System.out.println(entry);            }        }   }   ==============OUTPUT====== Hashmap Keys into list------> SriLanka Zimbabwe Nepal India Hashmap values into List-----> 400 600 800 700 Printing thorough iterator======> SriLanka=400 Zimbabwe=600 Nepal=800 India=700

 

Happy Learning :) 

Tricky question

 

In a social media application, You have a collection of posts, where each post can have multiple comments. 

To retrieve all the comments from all the posts and represents them as a single stream,
Which java Stream operation would you use?

 

The correct answer is flatmap().

So what is flatmap, flatMap() = Flattening + map()

It is an intermediate operation that is always lazy as described in Java Stream API

flattening means,  merging multiple collections/arrays into one.

OR,

Flattening is the process of converting several lists of lists and merge all those lists to create a single list containing all the elements from all the lists.

Flattening Example

Consider the following lists of lists:

Before Flattening: [[1, 2, 3, 4], [7, 8, 9, 0], [5, 6], [12, 18, 19, 20, 17], [22],[23,24,25,26,27]]

After Flattening: [1, 2, 3, 4, 7, 8, 9, 0, 5, 6, 12, 18, 19, 20, 17, 22,23,24,25,26,27]

Syntax

<R> Stream<R> flatMap(Function<? super T,? extends Stream<? extends R>> mapper)

• R represents the element type of the new stream.
• mapper is a non-interfering, stateless function to apply to each element which produces a stream of new values.
• The method returns a new stream of objects of type R.

Similar flatMap() Methods

IntStream flatMapToInt(Function<? super T,? extends IntStream> mapper)

LongStream flatMapToLong(Function<? super T,? extends LongStream> mapper)

DoubleStream flatMapToDouble(Function<? super T,? extends DoubleStream> mapper)

Some examples where flatMap can be used are:

Count of words of a text file.

Convert a Nested List into a single List.

Convert a Nested Array into a single Lis

How Many ways we can print Array in Java

 

Hi Friends,

Today i am going to show how many ways we can print Array in Java.

As we know following points:- 

Java array is a data structure where we can store the elements of the same data type.

The elements of an array are stored in a contiguous memory location. 

So, we can store a fixed set of elements in an array.

The index of an array starts from 0. 

there are following ways to print array:

How to change font size in Eclipse or STS for Java text editors?

 As Many of us face this issue, while using STS or Eclipse.

Also you you change theme Light to Dark mode then also need to change font size otherwise it would looks like very light.

So i am providing you steps to do it.

1.Go to Window tab of Eclipse or STS.

2.Click on Prefences

3.General → Appearance → Colors and Fonts → Java Editor text font

Please see below image and do the same.

Thanks,

Happy Learning