Java example source code file (ClassVersionChecker.java)

This example Java source code file (ClassVersionChecker.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

bufferedinputstream, bufferedwriter, error, exception, expected, file, filewriter, got, ioexception, nio, printwriter, regex, running, string, test, throwable, util

The ClassVersionChecker.java Java example source code

/*
 * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * @test
 * @bug 7157626 8001112
 * @summary Test major version for all legal combinations for -source and -target
 * @author sgoel
 *
 */

import java.io.*;
import java.nio.*;
import java.util.*;
import java.util.regex.*;

public class ClassVersionChecker {

    int errors;
    String[] jdk = {"","1.2","1.3","1.4","1.5","1.6","1.7","1.8"};
    File javaFile = null;

    public static void main(String[] args) throws Throwable {
        new ClassVersionChecker().run();
    }

    void run() throws Exception {
        writeTestFile();
        /* Rules applicable for -source and -target combinations
         * 1. If both empty, version num is for 1.7
         * 2. If source is not empty and target is empty, version is based on source
         * 3. If both non-empty, version is based on target
         */

        /* -source (0=>empty,1=>1.2,...) X -target (0=>empty,1=>1.2,...)
         * ver[0][0] => no -source or -target was given
         * -1 => invalid combinations
         */
        int[][] ver =
                {{52, -1, -1, -1, -1, -1, -1, -1},
                 {48, 46, 47, 48, 49, 50, 51, 52},
                 {48, 46, 47, 48, 49, 50, 51, 52},
                 {48, -1, -1, 48, 49, 50, 51, 52},
                 {52, -1, -1, -1, 49, 50, 51, 52},
                 {52, -1, -1, -1, -1, 50, 51, 52},
                 {52, -1, -1, -1, -1, -1, 51, 52},
                 {52, -1, -1, -1, -1, -1, -1, 52}};

        // Loop to run all possible combinations of source/target values
        for (int i = 0; i< ver.length; i++) {
            for (int j = 0 ; j< ver[i].length; j++) {
                if(ver[i][j] != -1) {
                    logMsg("Index values for i = " + i + " j = " + j);
                    logMsg("Running for src = " + jdk[i] + " target = "+jdk[j] +" expected = " + ver[i][j]);
                    test(i,j, ver[i][j]);
                }
            }
        }

        if (errors > 0)
            throw new Exception(errors + " errors found");
    }

    void test (int i, int j, int expected) {
        File classFile = compileTestFile(i, j, javaFile);
        short majorVer = getMajorVersion(classFile);
        checkVersion(majorVer, expected);
    }

    void writeTestFile() throws IOException {
        javaFile = new File("Test.java");
        try(PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(javaFile)));) {
            out.println("class Test { ");
            out.println("  public void foo() { }");
            out.println("}");
        } catch (IOException ioe) {
            error("IOException while creating Test.java" + ioe);
        }
    }

    File compileTestFile(int i , int j, File f) {
        int rc = -1;
        // Src and target are empty
        if (i == 0 && j == 0 ) {
            rc = compile("-g", f.getPath());
        } else if( j == 0 ) {  // target is empty
            rc = compile("-source", jdk[i], "-g", f.getPath());
        } else {
            rc = compile("-source", jdk[i], "-target", jdk[j], "-g", f.getPath());
        }
        if (rc != 0)
            throw new Error("compilation failed. rc=" + rc);
        String path = f.getPath();
        return new File(path.substring(0, path.length() - 5) + ".class");
    }

    int compile(String... args) {
        return com.sun.tools.javac.Main.compile(args);
    }

    void logMsg (String str) {
        System.out.println(str);
    }

    short getMajorVersion(File f) {
        List<String> args = new ArrayList();
        short majorVer = 0;
        try(DataInputStream in = new DataInputStream(new BufferedInputStream(new FileInputStream(f)));) {
            in.readInt();
            in.readShort();
            majorVer = in.readShort();
            System.out.println("major version:" +  majorVer);
        } catch (IOException e) {
            error("IOException while reading Test.class" + e);
        }
        return majorVer;
    }

    void checkVersion(short majorVer, int expected) {
        if (majorVer != expected ) {
            error("versions did not match, Expected: " + expected + "Got: " + majorVer);
        }
    }

    void error(String msg) {
       System.out.println("error: " + msg);
       errors++;
    }
}