Java JShell Import

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In this tutorial, we will learn how to work with import statements using JShell. We will also see how to import third-party library imports using JShell.

The Java Shell tool (JShell) is an interactive tool for learning the Java programming language and prototyping Java code. JShell is a Read-Evaluate-Print Loop (REPL), which evaluates declarations, statements, and expressions as they are entered and immediately shows the results.

Complete the Java JShell tutorial at https://www.javaguides.net/2022/06/java-shell-jshell-tutorial.html

Using Java Default Imports

By default, jshell imports some common packages on startup. You can type /imports command to see all the available imports:

jshell> /imports

|    import java.io.*

|    import java.math.*

|    import java.net.*

|    import java.nio.file.*

|    import java.util.*

|    import java.util.concurrent.*

|    import java.util.function.*

|    import java.util.prefs.*

|    import java.util.regex.*

|    import java.util.stream.*

The java.lang package contents are always available in JShell, just as in any Java source code file.

For example, we can use java.lang.String class methods using JShell:

Concatenate two string literals:

jshell> "java" + "guides"
$13 ==> "javaguides"

Check two String content equal using the equals() method:

jshell> "java".equals("java")
$14 ==> true

Using substring() method:

jshell> "java guides".substring(0, 4)

$15 ==> "java"

Java Import Different Package

In addition to the Java API packages, you can import other packages to use their types in JShell.

Let's import java.time package.

jshell> import java.time.*

Let's use the LocalDate class from the java.time package to print current date:

jshell> System.out.println(LocalDate.now())

2022-06-08

Use again /imports commands to see all the imports:

jshell> /imports

|    import java.io.*

|    import java.math.*

|    import java.net.*

|    import java.nio.file.*

|    import java.util.*

|    import java.util.concurrent.*

|    import java.util.function.*

|    import java.util.prefs.*

|    import java.util.regex.*

|    import java.util.stream.*

|    import java.time.*

Import Third-Party Packages

In order to import the third-party packages, you need first to use JShell’s /env-class-path command to add the packages to JShell’s CLASSPATH, which specifies where the additional packages are located. You can then use import declarations to experiment with the package contents in JShell.

Let’s add the Person class to JShell’s CLASSPATH. Also, I have downloaded a Gson library JAR file to add to CLASSPATH too so you can use the Gson class to generate a JSON-formatted text from the person class instance.

public class Person {

       private String name;

       public void setName(String name){

              this.name = name;
       }

       public String getName(){
              return name;
       }
}

Use the following command to add packages and libraries to the current JShell session’s CLASSPATH:

jshell> /env -class-path ./lib/gson-2.8.5.ja

   | Setting new options and restoring state.

The dot indicates the current folder from which you launched JShell. You also can specify complete paths to other folders on your system or the paths of JAR files that contain packages of compiled classes as I did here.

Conclusion

In this tutorial, we have seen how to work with import statements using JShell. We have also seen how to import third-party library imports using JShell.

Complete the Java JShell tutorial at https://www.javaguides.net/2022/06/java-shell-jshell-tutorial.html