Java Tutorial/Development/Java Compiler

Compile Java file

import javax.tools.Diagnostic;
import javax.tools.DiagnosticCollector;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
public class CompileFiles2 {
  public static void main(String[] args) {
    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
    DiagnosticCollector<JavaFileObject> dc;
    dc = new DiagnosticCollector<JavaFileObject>();
    StandardJavaFileManager sjfm;
    sjfm = compiler.getStandardFileManager(dc, null, null);
    Iterable<? extends JavaFileObject> fileObjects;
    fileObjects = sjfm.getJavaFileObjects(args);
    compiler.getTask(null, sjfm, dc, null, null, fileObjects).call();
    for (Diagnostic d : dc.getDiagnostics()) {
      System.out.println(d.getMessage(null));
      System.out.printf("Line number = %d\n", d.getLineNumber());
      System.out.printf("File = %s\n", d.getSource());
    }
  }
}

Compiler Info

import java.util.Set;
import javax.lang.model.SourceVersion;
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
public class CompilerInfo {
  public static void main(String[] args) {
    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
    System.out.println("Supported source versions:");
    Set<SourceVersion> srcVer = compiler.getSourceVersions();
    for (SourceVersion sv : srcVer)
      System.out.println("  " + sv.name());
    int nargs = compiler.isSupportedOption(args[0]);
    if (nargs == -1)
      System.out.println("Option " + args[0] + " is not supported");
    else
      System.out.println("Option " + args[0] + " takes " + nargs + " arguments");
  }
}

Compile String

import java.lang.reflect.Method;
import java.net.URI;
import java.util.Iterator;
import java.util.NoSuchElementException;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.SimpleJavaFileObject;
import javax.tools.ToolProvider;
public class CompileString {
  public static void main(String[] args) throws Exception {
    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
    String program = "class Test{" + "   public static void main (String [] args){"
        + "      System.out.println (\"Hello, World\");"
        + "      System.out.println (args.length);" + "   }" + "}";
    Iterable<? extends JavaFileObject> fileObjects;
    fileObjects = getJavaSourceFromString(program);
    compiler.getTask(null, null, null, null, null, fileObjects).call();
    Class<?> clazz = Class.forName("Test");
    Method m = clazz.getMethod("main", new Class[] { String[].class });
    Object[] _args = new Object[] { new String[0] };
    m.invoke(null, _args);
  }
  static Iterable<JavaSourceFromString> getJavaSourceFromString(String code) {
    final JavaSourceFromString jsfs;
    jsfs = new JavaSourceFromString("code", code);
    return new Iterable<JavaSourceFromString>() {
      public Iterator<JavaSourceFromString> iterator() {
        return new Iterator<JavaSourceFromString>() {
          boolean isNext = true;
          public boolean hasNext() {
            return isNext;
          }
          public JavaSourceFromString next() {
            if (!isNext)
              throw new NoSuchElementException();
            isNext = false;
            return jsfs;
          }
          public void remove() {
            throw new UnsupportedOperationException();
          }
        };
      }
    };
  }
}
class JavaSourceFromString extends SimpleJavaFileObject {
  final String code;
  JavaSourceFromString(String name, String code) {
    super(URI.create("string:///" + name.replace(".", "/") + Kind.SOURCE.extension), Kind.SOURCE);
    this.code = code;
  }
  public CharSequence getCharContent(boolean ignoreEncodingErrors) {
    return code;
  }
}

Enum Alternate Java Compilers

import java.util.ServiceLoader;
import javax.tools.JavaCompiler;
public class EnumAlternateJavaCompilers {
  public static void main(String[] args) {
    ServiceLoader<JavaCompiler> compilers;
    compilers = ServiceLoader.load(JavaCompiler.class);
    System.out.println(compilers.toString());
    for (JavaCompiler compiler : compilers)
      System.out.println(compiler);
  }
}

Get classpath using System class

public class Main {
  public static void main(String[] args) {
    System.out.println(System.getProperty("java.class.path"));
  }
}

JavaCompiler.run to compile

import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
public class CompileFiles1 {
  public static void main(String[] args) {
    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
    compiler.run(null, null, null, args);
  }
}

Programmatically compile Java class

import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
public class Main {
  public static void main(String[] args) {
    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
    int result = compiler.run(null, null, null, "Hello.java");
    System.out.println("Compile result code = " + result);
  }
}