97 lines
2.9 KiB
Java
97 lines
2.9 KiB
Java
/*
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* Copyright (C) 2017 The Gson authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.gson.internal;
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/**
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* Utility to check the major Java version of the current JVM.
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*/
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public final class JavaVersion {
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// Oracle defines naming conventions at http://www.oracle.com/technetwork/java/javase/versioning-naming-139433.html
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// However, many alternate implementations differ. For example, Debian used 9-debian as the version string
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private static final int majorJavaVersion = determineMajorJavaVersion();
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private static int determineMajorJavaVersion() {
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String javaVersion = System.getProperty("java.version");
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return getMajorJavaVersion(javaVersion);
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}
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// Visible for testing only
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static int getMajorJavaVersion(String javaVersion) {
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int version = parseDotted(javaVersion);
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if (version == -1) {
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version = extractBeginningInt(javaVersion);
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}
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if (version == -1) {
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return 6; // Choose minimum supported JDK version as default
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}
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return version;
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}
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// Parses both legacy 1.8 style and newer 9.0.4 style
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private static int parseDotted(String javaVersion) {
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try {
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String[] parts = javaVersion.split("[._]");
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int firstVer = Integer.parseInt(parts[0]);
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if (firstVer == 1 && parts.length > 1) {
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return Integer.parseInt(parts[1]);
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} else {
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return firstVer;
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}
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} catch (NumberFormatException e) {
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return -1;
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}
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}
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private static int extractBeginningInt(String javaVersion) {
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try {
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StringBuilder num = new StringBuilder();
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for (int i = 0; i < javaVersion.length(); ++i) {
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char c = javaVersion.charAt(i);
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if (Character.isDigit(c)) {
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num.append(c);
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} else {
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break;
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}
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}
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return Integer.parseInt(num.toString());
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} catch (NumberFormatException e) {
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return -1;
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}
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}
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/**
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* Gets the major Java version
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*
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* @return the major Java version, i.e. '8' for Java 1.8, '9' for Java 9 etc.
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*/
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public static int getMajorJavaVersion() {
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return majorJavaVersion;
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}
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/**
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* Gets a boolean value depending if the application is running on Java 9 or later
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*
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* @return {@code true} if the application is running on Java 9 or later; and {@code false} otherwise.
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*/
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public static boolean isJava9OrLater() {
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return majorJavaVersion >= 9;
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}
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private JavaVersion() { }
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}
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