为什么我要晒太阳。其他。争用符号找不到错误?

我有一个非常简单的程序:

Test.java

package com;
import sun.misc.Contended;
public class Test {
}

和 pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0                              http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>com</groupId>
<artifactId>Test</artifactId>
<version>1.0-SNAPSHOT</version>

<properties>
    <maven.compiler.source>1.9</maven.compiler.source>
    <maven.compiler.target>1.9</maven.compiler.target>
</properties>
</project>

当我把 mvn compile 我有:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.2:compile (default-compile) on project proj: Compilation failure
[ERROR] /home/john/Desktop/proj/src/main/java/com/Test.java: cannot find symbol
[ERROR] symbol:   class Contended
[ERROR] location: package sun.misc

为什么?