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Java example source code file (RealFunctionValidation.java)

This example Java source code file (RealFunctionValidation.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

applicationproperties, class, datainputstream, dataoutputstream, fileinputstream, illegalaccessexception, illegalargumentexception, ioexception, method, missingrequiredpropertyexception, object, reflection, string, stringbuilder, summarystatistics, util

The RealFunctionValidation.java Java example source code

 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *      http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

import org.apache.commons.math3.stat.descriptive.SummaryStatistics;
import org.apache.commons.math3.util.FastMath;

 * plot 'logGamma.dat' binary format="%double%double" endian=big u 1:2 w l
public class RealFunctionValidation {

    public static class MissingRequiredPropertyException
        extends IllegalArgumentException {

        private static final long serialVersionUID = 20121017L;

        public MissingRequiredPropertyException(final String key) {

            super("missing required property " + key);

    public static class ApplicationProperties {

        private static final int DOT = '.';

        private static final String METHOD_KEY = "method";

        private static final String SIGNATURE_KEY = "signature";

        private static final String INPUT_FILE_MASK = "inputFileMask";

        private static final String OUTPUT_FILE_MASK = "outputFileMask";

        private static final String FROM_KEY = "from";

        private static final String TO_KEY = "to";

        private static final String BY_KEY = "by";

        final Method method;

        final String inputFileMask;

        final String outputFileMask;

        final int from;

        final int to;

        final int by;

         * Returns a {@link Method} with specified signature.
         * @param className The fully qualified name of the class to which the
         * method belongs.
         * @param methodName The name of the method.
         * @param signature The signature of the method, as a list of parameter
         * types.
         * @return the method
         * @throws SecurityException
         * @throws ClassNotFoundException
        public static Method findStaticMethod(final String className,
                                              final String methodName,
                                              final List<Class signature)
            throws SecurityException, ClassNotFoundException {

            final int n = signature.size();
            final Method[] methods = Class.forName(className).getMethods();
            for (Method method : methods) {
                if (method.getName().equals(methodName)) {
                    final Class<?>[] parameters = method.getParameterTypes();
                    boolean sameSignature = true;
                    if (parameters.length == n) {
                        for (int i = 0; i < n; i++) {
                            sameSignature &= signature.get(i)
                        if (sameSignature) {
                            final int modifiers = method.getModifiers();
                            if ((modifiers & Modifier.STATIC) != 0) {
                                return method;
                            } else {
                                final String msg = "method must be static";
                                throw new IllegalArgumentException(msg);
            throw new IllegalArgumentException("method not found");

        public static Class<?> parsePrimitiveType(final String type) {

            if (type.equals("boolean")) {
                return Boolean.TYPE;
            } else if (type.equals("byte")) {
                return Byte.TYPE;
            } else if (type.equals("char")) {
                return Character.TYPE;
            } else if (type.equals("double")) {
                return Double.TYPE;
            } else if (type.equals("float")) {
                return Float.TYPE;
            } else if (type.equals("int")) {
                return Integer.TYPE;
            } else if (type.equals("long")) {
                return Long.TYPE;
            } else if (type.equals("short")) {
                return Short.TYPE;
            } else {
                final StringBuilder builder = new StringBuilder();
                builder.append(type).append(" is not a primitive type");
                throw new IllegalArgumentException(builder.toString());

        private static String getPropertyAsString(final Properties properties,
                                                  final String key) {

            final String value = properties.getProperty(key);
            if (value == null) {
                throw new MissingRequiredPropertyException(key);
            } else {
                return value;

        private static int getPropertyAsInteger(final Properties properties,
                                                final String key) {

            final String value = properties.getProperty(key);
            if (value == null) {
                throw new MissingRequiredPropertyException(key);
            } else {
                return Integer.parseInt(value);

        private ApplicationProperties(final String fullyQualifiedName,
                                      final String signature,
                                      final String inputFileMask,
                                      final String outputFileMask,
                                      final int from, final int to, final int by) {

            this.inputFileMask = inputFileMask;
            this.outputFileMask = outputFileMask;
            this.from = from;
            this.to = to;
            this.by = by;

            final String[] types = signature.split(",");
            final List<Class parameterTypes = new ArrayList>();
            for (String type : types) {
            final int index = fullyQualifiedName.lastIndexOf(DOT);
            try {
                final String className, methodName;
                className = fullyQualifiedName.substring(0, index);
                methodName = fullyQualifiedName.substring(index + 1);
                this.method = findStaticMethod(className, methodName,
            } catch (ClassNotFoundException e) {
                throw new IllegalArgumentException(e);


        public static final ApplicationProperties create(final Properties properties) {

            final String methodFullyQualifiedName;
            methodFullyQualifiedName = getPropertyAsString(properties,

            final String signature;
            signature = getPropertyAsString(properties, SIGNATURE_KEY);

            final String inputFileMask;
            inputFileMask = getPropertyAsString(properties, INPUT_FILE_MASK);

            final String outputFileMask;
            outputFileMask = getPropertyAsString(properties, OUTPUT_FILE_MASK);

            final int from = getPropertyAsInteger(properties, FROM_KEY);
            final int to = getPropertyAsInteger(properties, TO_KEY);
            final int by = getPropertyAsInteger(properties, BY_KEY);

            return new ApplicationProperties(methodFullyQualifiedName,
                                             signature, inputFileMask,
                                             outputFileMask, from, to, by);

    public static Object readAndWritePrimitiveValue(final DataInputStream in,
                                                    final DataOutputStream out,
                                                    final Class<?> type)
        throws IOException {

        if (!type.isPrimitive()) {
            throw new IllegalArgumentException("type must be primitive");
        if (type.equals(Boolean.TYPE)) {
            final boolean x = in.readBoolean();
            return Boolean.valueOf(x);
        } else if (type.equals(Byte.TYPE)) {
            final byte x = in.readByte();
            return Byte.valueOf(x);
        } else if (type.equals(Character.TYPE)) {
            final char x = in.readChar();
            return Character.valueOf(x);
        } else if (type.equals(Double.TYPE)) {
            final double x = in.readDouble();
            return Double.valueOf(x);
        } else if (type.equals(Float.TYPE)) {
            final float x = in.readFloat();
            return Float.valueOf(x);
        } else if (type.equals(Integer.TYPE)) {
            final int x = in.readInt();
            return Integer.valueOf(x);
        } else if (type.equals(Long.TYPE)) {
            final long x = in.readLong();
            return Long.valueOf(x);
        } else if (type.equals(Short.TYPE)) {
            final short x = in.readShort();
            return Short.valueOf(x);
        } else {
            // This should never occur.
            throw new IllegalStateException();

    public static SummaryStatistics assessAccuracy(final Method method,
                                                   final DataInputStream in,
                                                   final DataOutputStream out)
        throws IOException, IllegalAccessException, IllegalArgumentException,
        InvocationTargetException {

        if (method.getReturnType() != Double.TYPE) {
            throw new IllegalArgumentException("method must return a double");

        final Class<?>[] types = method.getParameterTypes();
        for (int i = 0; i < types.length; i++) {
            if (!types[i].isPrimitive()) {
                final StringBuilder builder = new StringBuilder();
                builder.append("argument #").append(i + 1)
                    .append(" of method ").append(method.getName())
                    .append("must be of primitive of type");
                throw new IllegalArgumentException(builder.toString());

        final SummaryStatistics stat = new SummaryStatistics();
        final Object[] parameters = new Object[types.length];
        while (true) {
            try {
                for (int i = 0; i < parameters.length; i++) {
                    parameters[i] = readAndWritePrimitiveValue(in, out,
                final double expected = in.readDouble();
                if (FastMath.abs(expected) > 1E-16) {
                    final Object value = method.invoke(null, parameters);
                    final double actual = ((Double) value).doubleValue();
                    final double err = FastMath.abs(actual - expected);
                    final double ulps = err / FastMath.ulp(expected);
            } catch (EOFException e) {
        return stat;

    public static void run(final ApplicationProperties properties)
        throws IllegalAccessException, IllegalArgumentException,
        InvocationTargetException, IOException {

        for (int i = properties.from; i < properties.to; i += properties.by) {
            final String inputFileName;
            inputFileName = String.format(properties.inputFileMask, i);
            final String outputFileName;
            outputFileName = String.format(properties.outputFileMask, i);

            final DataInputStream in;
            in = new DataInputStream(new FileInputStream(inputFileName));
            final DataOutputStream out;
            out = new DataOutputStream(new FileOutputStream(outputFileName));

            final SummaryStatistics stats;
            stats = assessAccuracy(properties.method, in, out);

            System.out.println("input file name = " + inputFileName);
            System.out.println("output file name = " + outputFileName);

    public static void main(final String[] args)
        throws IOException, IllegalAccessException, IllegalArgumentException,
        InvocationTargetException {

        if (args.length == 0) {
            final String msg = "missing required properties file";
            throw new IllegalArgumentException(msg);

        final FileInputStream in = new FileInputStream(args[0]);
        final Properties properties = new Properties();

        final ApplicationProperties p;
        p = ApplicationProperties.create(properties);


Other Java examples (source code examples)

Here is a short list of links related to this Java RealFunctionValidation.java source code file:

my book on functional programming


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