Category Archives: Core Java

We will discuss commonly asked questions related to java 8 , exception handling, string operations, java io etc.

Java Scanner example – read & write contents to/ from file (example)

Scanner is text parser which used to parse primitives & strings using regular expression. Scanner split the input into token using delimiter pattern. Default pattern delimiter is whitespace. We will write content to a file using FileWriter class. Then, we will read content from as file using Scanner class. Scanner class extends object & implements… Read More »

Inter thread communication in java (Example/ PipedInputStream /PipedOutputStream)

Inter thread communication is very common phenomenon. There are many ways to achieve inter thread communication. In current post, we will use pipes to achieve thread communication. Java has set of classes named PipedOutputStream & PipedInputStream to communicate between threads. We will create couple of threaders namely producer & consumer. Producer thread will produce the… Read More »

Unzip or decompress files in java using ZipInputStream & ZipEntry (example)

Given a zipped or compressed file in java. Write a program to unzip or decompress the contents of zip file using ZipInputStream in java. Zip file may contain nested directory structure. e.g. Zip file may have compressed files having following directory structure. FirstFile.txt SecondFile.txt Dir1\Dir1_F1.txt Dir1\Dir1_F2.txt Dir1\Dir11\Dir11_F1.txt Dir1\Dir11\Dir11_F2.txt ….. Read the content of zip files… Read More »

Generate UUID or GUID from String in java (with example)

Given an string representing unique identifier. We would like to convert string to corresponding universal unique identifier (UUID) or Globally unique identifier (GUID). We will use java.util.UUID class to create UUID or GUID from string. e.g UUID generateUUID = UUID.fromString(inputUUID) Program: generate UUID or GUID from String in java package org.learn.uuid; import java.util.UUID; public class GenerateUUIDFromString {… Read More »