JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2012, 2019, 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.
 */


package org.graalvm.compiler.debug;

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import jdk.vm.ci.services.Services;

/** Avoid using directly. Only public for the needs of unit testing. */
public final class Versions {
    static final Versions VERSIONS;
    static {
        String home = Services.getSavedProperties().get("java.home");
        VERSIONS = new Versions(home == null ? null : new File(home).toPath());
    }

    private final Map<Object, Object> versions;

    public Versions(Path home) {
        Map<Object, Object> map = new HashMap<>();
        ASSIGN: try {
            Path info = findReleaseInfo(home);
            if (info == null) {
                break ASSIGN;
            }
            for (String line : Files.readAllLines(info)) {
                final String prefix = "SOURCE=";
                if (line.startsWith(prefix)) {
                    for (String versionInfo : line.substring(prefix.length()).replace('"', ' ').split(" ")) {
                        String[] idVersion = versionInfo.split(":");
                        if (idVersion != null && idVersion.length == 2) {
                            map.put("version." + idVersion[0], idVersion[1]);
                        }
                    }
                    break ASSIGN;
                }
            }
        } catch (IOException ex) {
            // no versions file found
        }
        versions = Collections.unmodifiableMap(map);
    }

    public Map<Object, Object> withVersions(Map<Object, Object> properties) {
        if (properties == null) {
            return versions;
        } else {
            properties.putAll(versions);
            return properties;
        }
    }

    private static Path findReleaseInfo(Path jreDir) {
        if (jreDir == null) {
            return null;
        }

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