blocks|key|19986|text|您可以通过读取java系统属性以编程方式完成此操作|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|19987|@Test
public+void+javaVersion()+{
++++System.out.println(System.getProperty("java.version"));
++++System.out.println(System.getProperty("java.runtime.version"));
++++System.out.println(System.getProperty("java.home"));
++++System.out.println(System.getProperty("java.vendor"));
++++System.out.println(System.getProperty("java.vendor.url"));
++++System.out.println(System.getProperty("java.class.path"));
}|code-block|syntax|javascript|19988|这将输出一些内容，如|19989|1.7.0_17
1.7.0_17-b02
C:\workspaces\Oracle\jdk1.7\jre
Oracle+Corporation
http://java.oracle.com/
C:\workspaces\Misc\Miscellaneous\bin;+...|19990|第一行显示版本号。你可以解析它，看看它是否适合你最低要求的java版本。您可以找到有关命名约定here和更多信息here的说明。|19991|entityMap|0|LINK|mutability|MUTABLE|url|http://www.oracle.com/technetwork/java/javase/versioning-naming-139433.html|1|http://www.oracle.com/technetwork/java/javase/overview/jdk-version-number-scheme-1918258.html^0|7|4|0|0|0|0|1B|4|0|1K|4|1|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|14|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|16|8|@]|D|@$9|17|A|18|1|19]|$9|1A|A|1B|1|1C]]|E|$]]|$1|Q|3|-4|5|6|7|1D|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|Z]]]]

You can do it programmatically by reading the <code>java</code> system properties

<pre><code>@Test
public void javaVersion() {
 System.out.println(System.getProperty("java.version"));
 System.out.println(System.getProperty("java.runtime.version"));
 System.out.println(System.getProperty("java.home"));
 System.out.println(System.getProperty("java.vendor"));
 System.out.println(System.getProperty("java.vendor.url"));
 System.out.println(System.getProperty("java.class.path"));
}
</code></pre>

This will output somthing like

<pre><code>1.7.0_17
1.7.0_17-b02
C:\workspaces\Oracle\jdk1.7\jre
Oracle Corporation
http://java.oracle.com/
C:\workspaces\Misc\Miscellaneous\bin; ...
</code></pre>

The first line shows the version number. You can parse it an see whether it fits your minimun required java version or not. You can find a description for the naming convention <a href="http://www.oracle.com/technetwork/java/javase/versioning-naming-139433.html" rel="noreferrer">here</a> and more infos <a href="http://www.oracle.com/technetwork/java/javase/overview/jdk-version-number-scheme-1918258.html" rel="noreferrer">here</a>.

blocks|key|19942|text|打开命令提示符，键入以下命令：java+-version|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|19943|在成功执行时，该命令将输出Java版本以及Java+Environment的内部版本和Java+HotSpot客户端VM的内部版本。|19944|​|19945|📷|atomic|19946|19947|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/0e00c1f033c4ba0f14b520627f373456.png|imageAlt^0|F|D|0|0|0|0|1|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|10|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|11|8|@]|D|@$9|12|A|13|1|14]]|E|$]]|$1|M|3|I|5|6|7|15|8|@]|D|@]|E|$]]|$1|N|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|O|$P|$5|Q|R|S|E|$T|U|V|-4]]]]

Open Command Prompt and type in the following command: <code>java -version</code>

Upon successful execution, the command will output the version of Java along with Java SE Runtime Environment’s build and Java HotSpot Client VM’s build.

<img src="https://i.stack.imgur.com/3gjVX.png" alt="enter image description here">

blocks|key|236251|text|转到此链接并等待一段时间以加载。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|236252|http://www.java.com/en/download/testjava.jsp|offset|length|236253|您将看到下图：|236254|📷|atomic|236255|​|236256|也可以打开命令窗口，然后键入java+-version|style|CODE|236257|entityMap|0|LINK|mutability|MUTABLE|url|1|IMAGE|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/e306a23ce9143da63afdd69cc7df9ebd.png|imageAlt^0|0|0|18|0|0|0|0|1|1|0|0|E|D|0^^$0|@$1|2|3|4|5|6|7|13|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|14|8|@]|9|@$D|15|E|16|1|17]]|A|$]]|$1|F|3|G|5|6|7|18|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|19|8|@]|9|@$D|1A|E|1B|1|1C]]|A|$]]|$1|K|3|L|5|6|7|1D|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|1E|8|@$D|1F|E|1G|O|P]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|C]]|X|$5|Y|U|Z|A|$10|11|12|-4]]]]

Go to this link and wait for a while to load.

<a href="http://www.java.com/en/download/testjava.jsp" rel="nofollow noreferrer">http://www.java.com/en/download/testjava.jsp</a>

You will see the below image:
<img src="https://i.stack.imgur.com/t9NzX.png" alt="enter image description here">

You can alternatively open command window and type <code>java -version</code>

blocks|key|20061|text|1)根据您的操作系统打开命令提示符或终端。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|20062|2)然后在终端输入java+--version。|offset|length|style|CODE|20063|3)如果java安装成功，会显示相应的版本。|20064|entityMap^0|0|9|E|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@$D|N|E|O|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|P|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|K|$]]

1)Open the command prompt or terminal based on your OS.

2)Then type <code>java --version</code> in the terminal.

3) If java is installed successfullly it will show the respective version .

blocks|key|236285|text|安装Java后，在环境变量中设置路径，然后打开命令提示符并输入java+-version。如果安装正确，它将列出java版本、jre版本等。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|236286|此外，您还可以尝试使用javac命令进行检查。如果它显示了一些数据，那么你的java已经安装了正确的路径设置，否则它就会认为javac是一个无效的命令。|236287|entityMap^0|V|D|0|B|5|1Q|5|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|R|8|@]|D|@]|E|$]]]|I|$]]

After installing Java, set the path in environmental variables and then open the command prompt and type <code>java -version</code>. If installed properly, it'll list the java version, jre version, etc.

You can additionally check by trying the <code>javac</code> command too. If it displays some data, you've your java installed with the proper path set, else it'll that <code>javac</code> is an invalid command.

blocks|key|236337|text|在命令窗口中键入|type|unstyled|depth|inlineStyleRanges|entityRanges|data|236338|java+-version|code-block|syntax|javascript|236339|如果它给出一个输出，那么一切都会很好。如果你想开发软件，你可能想要设置路径。|236340|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Type in the command window

<pre><code>java -version
</code></pre>

If it gives an output everything should be fine. If you want to develop software you might want to set the PATH.

blocks|key|236444|text|检查java文件夹的安装目录(通常是C:\Program+Files+(x86)或C:\Program+Files)。如果它包含您已安装的java的JRE。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|236445|entityMap^0|I|M|15|G|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

Check the installation directories (typically <code>C:\Program Files (x86)</code> or <code>C:\Program Files</code>) for the java folder. If it contains the JRE you have java installed.

blocks|key|236487|text|使用Apache+Commons-Lang的SystemUtils.isJavaVersionAtLeast(JavaVersion)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|236488|import+org.apache.commons.lang3.JavaVersion;
import+org.apache.commons.lang3.SystemUtils;

if+(SystemUtils.isJavaVersionAtLeast(JavaVersion.JAVA_1_8)
++++System.out.println("Java+version+was+8+or+greater!");|code-block|syntax|javascript|236489|entityMap|0|LINK|mutability|MUTABLE|url|https://commons.apache.org/proper/commons-lang/javadocs/api-3.1/org/apache/commons/lang3/SystemUtils.html#isJavaVersionAtLeast(org.apache.commons.lang3.JavaVersion)^0|M|19|M|19|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

Using Apache Commons-Lang's <a href="https://commons.apache.org/proper/commons-lang/javadocs/api-3.1/org/apache/commons/lang3/SystemUtils.html#isJavaVersionAtLeast(org.apache.commons.lang3.JavaVersion)" rel="nofollow noreferrer"><code>SystemUtils.isJavaVersionAtLeast(JavaVersion)</code></a>

<pre><code>import org.apache.commons.lang3.JavaVersion;
import org.apache.commons.lang3.SystemUtils;

if (SystemUtils.isJavaVersionAtLeast(JavaVersion.JAVA_1_8)
 System.out.println("Java version was 8 or greater!");
</code></pre>

blocks|key|20104|text|如果java尚未安装，请执行以下操作。则不能运行由java编写的程序来检查是否安装了java。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|20105|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

If java not installed yet. Then program written by java cannot be run to check if java is installed or not.

I am trying to install java windows application on client machine.I want to check whether
requried JRE is installed on the machine or not. I want to check it by java program not by cmd command

How to check whether java is installed on the computer

我正在尝试在客户机上安装java windows应用程序，我想检查机器上是否安装了所需的JRE。我想用java程序检查，而不是cmd命令。

问如何检查计算机上是否安装了java
EN

回答 9

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问如何检查计算机上是否安装了javaEN

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问如何检查计算机上是否安装了java
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