In the first article, » Getting Started with R Using Java , » we started with installing R and installing the rJava package. We discussed initializing the JVM, setting the classpath, creating a Java object, and calling a Java method. In this tutorial, we shall discuss the rJava package to use Java Strings and the Swing Java API from R. This tutorial has the following sections:
Using Strings was introduced by creating a new object from the java.lang. String class and a supplied String as constructor arg.
The jstrVal function could be used to output the String value.
Any of the String class methods could be called by using the String object « s ». As an example, call the instance method indexOf(String str) to find the index of a substring such as « Hello. »
The return value is an int with a value of 0, indicating the index of « Hello » in « Hello String! »
Alternatively, the short form could be used to call the indexOf(String str) method as follows to output int 0.
The R Console output from the preceding method calls is as follows, as shown in Figure 1.
Figure 1: R Console output from the preceding method calls
As an example, call the static method valueOf(int i) in the String class.
The int value as a String is returned.
The R Console output from the preceding command is shown (see Figure 2).
Figure 2: The R Console output from the preceding command
As another example, call the concat(String str) method in the java.lang. String class using the.jcall(obj, returnSig = « V », method, …) function, supplying the object reference as the « s » String object used from the start in this tutorial, a return type signature for the String class, and the method to call as « concat » with the « s » object reference as the concat method arg.
The value output is the Strings concatenated.
The output from the preceding function call is shown in R Console, as referenced in Figure 3.
Figure 3: The output from the preceding function call, shown in R Console
A new String class reference could be created by using the J high level API, as follows.
