Most interesting/useful Java classes? [closed]

Answer 1

Since you specifically mentioned JDK, I think it's allowed to mention an API which actually isn't available in the JRE and is also less known among most of us: javax.tools.

Here's a full demo snippet:

package test;

import java.io.File;
import java.io.FileWriter;
import java.io.Writer;
import java.net.URL;
import java.net.URLClassLoader;

import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;

public class Test {

    public static void main(String[] args) throws Exception {
        // Prepare source somehow.
        String source = "public class Test { static { System.out.println(\"test\"); } }";

        // Save source in .java file.
        File root = new File("/test");
        File sourceFile = new File(root, "Test.java");
        Writer writer = new FileWriter(sourceFile);
        writer.write(source);
        writer.close();

        // Compile source file.
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        compiler.run(null, null, null, sourceFile.getPath());

        // Load compiled class.
        URLClassLoader classLoader = URLClassLoader.newInstance(new URL[] { root.toURI().toURL() });
        Class cls = Class.forName("Test", true, classLoader); // Prints "test".
    }
}

Useful? Not sure. Interesting? Yes, interesting to know :)

For the remnant, I like the Collections, Reflection, Concurrent and JDBC API's. All of which are already mentioned before here.