steps to follow:

1. Download javax.json jar file.

2. As you have downloaded this jar file, specify it in java compiler classpath, using javac -classpath key.

3. As you have your code compiled, then use -cp key for java command to specify this jar file in the runtime classpath upon your code execution.

More detailed information on classpath settings can be found here: http://kevinboone.net/classpath.html

It's included in Java EE 7 (not SE 7/8)

When compiling, you must specify the absolute path to the .jar file which contains the package with its classes, like this:

javac -cp /usr/share/java/json-20160212.jar JsonParser.java

According to the official documentation from Oracle about PATH and CLASSPATH variables:

The preferred way to specify the class path is by using the -cp command line switch. This allows the CLASSPATH to be set individually for each application without affecting other applications. Setting the CLASSPATH can be tricky and should be performed with care.

The default value of the class path is ".", meaning that only the current directory is searched. Specifying either the CLASSPATH variable or the -cp command line switch overrides this value.

If using Maven, add this dependency to your pom.xml

<dependency>
    <groupId>javax.json</groupId>
    <artifactId>javax.json-api</artifactId>
    <version>1.0</version>
</dependency>

For Gradle, add this to your build.gradle

compile 'javax.json:javax.json-api:1.0'

include the following dependency in your "pom.xml" file.

<dependency>
    <groupId>com.googlecode.json-simple</groupId>
    <artifactId>json-simple</artifactId>
    <version>1.1.1</version>
</dependency>

I have to download and add to my lib; javax.json-1.0.4.jar which gives me the Json Processing capability that I needed.

In my case i was using maven build tool and got this error so had to add below dependency from here like below and error resolved.

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20180130</version>
</dependency>