blocks|key|1283847|text|如何从包meta+infos中获取版本：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1283848|String+version+=+Runtime.class.getPackage().getImplementationVersion();|code-block|syntax|javascript|1283849|打印出类似以下内容：|1283850|1.7.0_13|1283851|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

What about getting the version from the package meta infos:

<pre><code>String version = Runtime.class.getPackage().getImplementationVersion();
</code></pre>

Prints out something like:

1.7.0_13

blocks|key|1283901|text|Runtime.version()|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1283902|从Java9开始，可以使用返回Runtime.Version的Runtime.version()|1283903|Runtime.Version+version+=+Runtime.version();|code-block|syntax|javascript|1283904|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/lang/Runtime.Version.html|1|https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/lang/Runtime.html#version())^0|0|H|0|F|F|V|H|F|F|0|V|H|1|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]]|D|@$9|14|A|15|1|16]|$9|17|A|18|1|19]]|E|$]]|$1|H|3|I|5|J|7|1A|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|1B|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]|U|$5|P|Q|R|E|$S|V]]]]

<h1><code>Runtime.version()</code></h1>
Since Java 9, you can use <a href="https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/lang/Runtime.html#version()" rel="noreferrer"><code>Runtime.version()</code></a>, which returns a <a href="https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/lang/Runtime.Version.html" rel="noreferrer"><code>Runtime.Version</code></a>:
<pre><code>Runtime.Version version = Runtime.version();
</code></pre>

blocks|key|1283939|text|只需注意，在Java+9和更高版本中，命名约定是不同的。System.getProperty("java.version")返回"9"而不是"1.9"。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1283940|entityMap^0|S|Y|1S|3|1Y|5|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

Just a note that in Java 9 and above, the naming convention is different. <code>System.getProperty("java.version")</code> returns <code>"9"</code> rather than <code>"1.9"</code>.

blocks|key|1283798|text|不工作，需要--pos来评估double：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1283799|++++String+version+=+System.getProperty("java.version");
++++System.out.println("version:"+%2B+version);
++++int+pos+=+0,+count+=+0;
++++for+(;+pos+<+version.length()+&&+count+<+2;+pos%2B%2B)+{
++++++++if+(version.charAt(pos)+==+'.')+{
++++++++++++count%2B%2B;
++++++++}
++++}

++++--pos;+//EVALUATE+double

++++double+dversion+=+Double.parseDouble(version.substring(0,+pos));
++++System.out.println("dversion:"+%2B+dversion);
++++return+dversion;
}|code-block|syntax|javascript|1283800|entityMap^0|6|5|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Does not work, need <code>--pos</code> to evaluate double:

<pre><code> String version = System.getProperty("java.version");
 System.out.println("version:" + version);
 int pos = 0, count = 0;
 for (; pos &lt; version.length() &amp;&amp; count &lt; 2; pos++) {
 if (version.charAt(pos) == '.') {
 count++;
 }
 }

 --pos; //EVALUATE double

 double dversion = Double.parseDouble(version.substring(0, pos));
 System.out.println("dversion:" + dversion);
 return dversion;
}
</code></pre>

blocks|key|1283872|text|Apache+Commons+Lang示例：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1283873|import+org.apache.commons.lang.SystemUtils;

++++Float+version+=+SystemUtils.JAVA_VERSION_FLOAT;

++++if+(version+<+1.4f)+{+
++++++++//+legacy
++++}+else+if+(SystemUtils.IS_JAVA_1_5)+{
++++++++//+1.5+specific+code
++++}+else+if+(SystemUtils.isJavaVersionAtLeast(1.6f))+{
++++++++//+1.6+compatible+code
++++}+else+{
++++++++//+dodgy+clause+to+catch+1.4+:)
++++}|code-block|syntax|javascript|1283874|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Example for Apache Commons Lang:

<pre><code>import org.apache.commons.lang.SystemUtils;

 Float version = SystemUtils.JAVA_VERSION_FLOAT;

 if (version &lt; 1.4f) { 
 // legacy
 } else if (SystemUtils.IS_JAVA_1_5) {
 // 1.5 specific code
 } else if (SystemUtils.isJavaVersionAtLeast(1.6f)) {
 // 1.6 compatible code
 } else {
 // dodgy clause to catch 1.4 :)
 }
</code></pre>

blocks|key|1283980|text|如果您可以依赖于apache+utils，则可以使用org.apache.commons.lang3.SystemUtils。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1283981|++++System.out.println("Is+Java+version+at+least+1.8:+"+%2B+SystemUtils.isJavaVersionAtLeast(JavaVersion.JAVA_1_8));|code-block|syntax|javascript|1283982|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you can have dependency to apache utils you can use org.apache.commons.lang3.SystemUtils.

<pre><code> System.out.println("Is Java version at least 1.8: " + SystemUtils.isJavaVersionAtLeast(JavaVersion.JAVA_1_8));
</code></pre>

blocks|key|1069377|text|下面是用JOSM实现的代码|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1069378|/**
+*+Returns+the+Java+version+as+an+int+value.
+*+@return+the+Java+version+as+an+int+value+(8,+9,+etc.)
+*+@since+12130
+*/
public+static+int+getJavaVersion()+{
++++String+version+=+System.getProperty("java.version");
++++if+(version.startsWith("1."))+{
++++++++version+=+version.substring(2);
++++}
++++//+Allow+these+formats:
++++//+1.8.0_72-ea
++++//+9-ea
++++//+9
++++//+9.0.1
++++int+dotPos+=+version.indexOf('.');
++++int+dashPos+=+version.indexOf('-');
++++return+Integer.parseInt(version.substring(0,
++++++++++++dotPos+>+-1+?+dotPos+:+dashPos+>+-1+?+dashPos+:+1));
}|code-block|syntax|javascript|1069379|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/openstreetmap/josm/blob/a3a6e8a6b657cf4c5b4c64ea14d6e87be6280d65/src/org/openstreetmap/josm/tools/Utils.java#L1566-L1585^0|4|4|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Here's the implementation in <a href="https://github.com/openstreetmap/josm/blob/a3a6e8a6b657cf4c5b4c64ea14d6e87be6280d65/src/org/openstreetmap/josm/tools/Utils.java#L1566-L1585" rel="noreferrer">JOSM</a>:

<pre><code>/**
 * Returns the Java version as an int value.
 * @return the Java version as an int value (8, 9, etc.)
 * @since 12130
 */
public static int getJavaVersion() {
 String version = System.getProperty("java.version");
 if (version.startsWith("1.")) {
 version = version.substring(2);
 }
 // Allow these formats:
 // 1.8.0_72-ea
 // 9-ea
 // 9
 // 9.0.1
 int dotPos = version.indexOf('.');
 int dashPos = version.indexOf('-');
 return Integer.parseInt(version.substring(0,
 dotPos &gt; -1 ? dotPos : dashPos &gt; -1 ? dashPos : 1));
}
</code></pre>

blocks|key|1283776|text|我不知道检查这一点的另一种方法，但这里:+http://java.sun.com/j2se/1.5.0/docs/api/java/lang/System.html#getProperties()(http://java.sun.com/j2se/1.5.0/docs/api/java/lang/System.html#getProperties(%2529)“暗示"java.version”是一个标准系统属性，所以我希望它能与其他JVM一起工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1283777|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/j2se/1.5.0/docs/api/java/lang/System.html#getProperties(%2529)^0|2R|28|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Don't know another way of checking this, but this: <a href="http://java.sun.com/j2se/1.5.0/docs/api/java/lang/System.html#getProperties()" rel="nofollow noreferrer"><a href="http://java.sun.com/j2se/1.5.0/docs/api/java/lang/System.html#getProperties()" rel="nofollow noreferrer">http://java.sun.com/j2se/1.5.0/docs/api/java/lang/System.html#getProperties()</a>"</a> implies "java.version" is a standard system property so I'd expect it to work with other JVMs.

blocks|key|1069356|text|下面是@mvanle的答案，转换为Scala：scala>+val+Array(javaVerPrefix,+javaVerMajor,+javaVerMinor,+_,+_)+=+System.getProperty("java.runtime.version").split("\\.%7C_%7C-b")+javaVerPrefix:+String+=+1+javaVerMajor:+String+=+8+javaVerMinor:+String+=+0|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1069357|entityMap^0|N|5O|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

Here is the answer from @mvanle, converted to Scala:
<code>
scala&gt; val Array(javaVerPrefix, javaVerMajor, javaVerMinor, _, _) = System.getProperty("java.runtime.version").split("\\.|_|-b")
javaVerPrefix: String = 1
javaVerMajor: String = 8
javaVerMinor: String = 0
</code>

blocks|key|1069400|text|在kotlin：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1069401|/**
+*+Returns+the+major+JVM+version,+e.g.+6+for+Java+1.6,+8+for+Java+8,+11+for+Java+11+etc.
+*/
public+val+jvmVersion:+Int+get()+=+System.getProperty("java.version").parseJvmVersion()

/**
+*+Returns+the+major+JVM+version,+1+for+1.1,+2+for+1.2,+3+for+1.3,+4+for+1.4,+5
+*+for+1.5+etc.
+*/
fun+String.parseJvmVersion():+Int+{
++++val+version:+String+=+removePrefix("1.").takeWhile+{+it.isDigit()+}
++++return+version.toInt()
}|code-block|syntax|javascript|1069402|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

In kotlin:
<pre class="lang-kotlin prettyprint-override"><code>/**
 * Returns the major JVM version, e.g. 6 for Java 1.6, 8 for Java 8, 11 for Java 11 etc.
 */
public val jvmVersion: Int get() = System.getProperty(&quot;java.version&quot;).parseJvmVersion()

/**
 * Returns the major JVM version, 1 for 1.1, 2 for 1.2, 3 for 1.3, 4 for 1.4, 5
 * for 1.5 etc.
 */
fun String.parseJvmVersion(): Int {
 val version: String = removePrefix(&quot;1.&quot;).takeWhile { it.isDigit() }
 return version.toInt()
}
</code></pre>

I need to work around a Java bug in JDK 1.5 which was fixed in 1.6. I'm using the following condition:

<pre><code>if (System.getProperty("java.version").startsWith("1.5.")) {
 ...
} else {
 ...
}
</code></pre>

Will this work for other JVMs? Is there a better way to check this?

Getting Java version at runtime

我需要解决JDK1.5中的一个Java错误，该错误已在1.6中修复。我使用以下条件：if (System.getProperty("java.version").startsWith("1.5.")) {    ...} else {    ...}这是否适用于其他JVM？有没有更好的方法来检查这个？

问在运行时获取Java版本
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