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Friday, July 3, 2015

How to Convert Fahrenheit to Celsius in Java with Example

In this Java tutorial, you will learn how to write a program to convert Fahrenheit to Celsius in Java. Fahrenheit is a thermodynamic temperature scale, where the freezing point of water is 32 degrees Fahrenheit (°F) and the boiling point of water is 212°F (at standard atmospheric pressure). This puts the boiling and freezing points of water exactly 180 degrees apart. Therefore, a degree on the Fahrenheit scale is 1/180 of the interval between the freezing point and the boiling point of water. Absolute zero is defined as -459.67°F. If you know, in Celsius scale, freezing point of water is at 0ºC and boiling point of water is at 100ºC. By using these fact, you can easily deduce a formula to convert Fahrenheit temperature into Celsius. To be frank, if you have been a Science student you already know about that formula, nothing new about it. What is more important is to learn how to convert such formula into a computer program using Java programming language. This is what you will learn in this tutorial. BTW, if you an absolute Java beginner and learning Java, I suggest you to take a look at couple of introductory books about Java programming language e.g. Java: A Beginner's guide by Herbert Schildt, its one of the up-to-date book in Java and covers even latest Java release, Java 8. If you are one who like to try couple of books before settling it for one then you can also check here for couple of more recommended books for Java beginners.

Thursday, July 2, 2015

How to solve java.lang.UnsatisfiedLinkError: no ocijdbc11 in Java

"java.lang.unsatisfiedlinkerror no ocijdbc11 in java.library.path" error comes when you try to connect to Oracle 11g database using OCI (thick) driver by using tns name, but ocijdbc11.dll file is not available in PATH or java.library.path environment variable. ocijdbc11.dll is a native library and if you know Java searches native library in PATH or a location specified by java.library.path system property, if it doesn't find the dll, then it throws java.lang.unsatisfiedlinkerror no ocijdbc11 in java.library.path error. This dll is usually find in C:\Programs\Oracle\ora11g\bin\ocijdbc11.dll, but it could vary depending upon your Oracle installation. First step to solve this error is search for this dll in your machine, if you are using windows, just search in your C drive. If the dll is not there then you need to download that from Oracle's website. If its already present then just add its location into PATH variable. If you are explicitly providing java.library.path then also provide it there e.g.
-Djava.library.path=C:\Programs\Oracle\ora11g\bin\ocijdbc11.dll .

Wednesday, July 1, 2015

How to use wait, notify and notifyAll in Java - Producer Consumer Example

You can use wait, notify and notifyAll methods to communicate between threads in Java. For example, if you have two threads running in your program e.g.Producer and Consumer then producer thread can communicate to consumer that it can start consuming now because there are items to consume in queue. Similarly a consumer thread can tell producer that it can also start putting items now because there is some space in queue, which is created as a result of consumption. A thread can use wait() method to pause and do nothing depending upon some condition. For example, in producer consumer problem, producer thread should wait if queue is full and consumer thread should wait if queue is empty. If some thread is waiting for some condition to become true, you can use notify and notifyAll methods to inform them that condition is now changed and they can wake up. Both notify() and notifyAll() method sends notification but notify sends notification to only one of the waiting thread, no guarantee which thread will receive notification and notifyAll() sends notification to all threads. So if only one thread is waiting on an object lock, also known as monitor then both notify and notifyAll wil send notification to it. If multiple threads are waiting on a monitor then notify will only inform one of the lucky thread and rest will not receive any notification, but notifyAll will inform all threads. In this Java multi-threading tutorial you will learn how to use wait, notify and notifyAll() method in Java to implement inter thread communication by solving producer consumer problem. BTW, if you are serious about mastering concurrency and multi-threading, I strongly suggest you to read Java Concurrency in Practice by Brian Goetz, without reading that book your journey to Java multi-threading is not complete. Its probably one of the most recommended book to Java developers.