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Support different versions of the same dependency

The framework I am developing on has to support 2 versions of the same library. Those versions contain breaking changes, but we don't need those parts! What we would like now is to guarantee that those methods are never called on accident.
e.g.
guava 18.0 HostAndPort.from("127.0.0.1").getHostText()
guava 23.0 HostAndPort.from("127.0.0.1").getHost()
Is there any way to ensure that such breaking methods are never called for future commits without manually checking each commit?
What we have done so far is, that we provide the library in version 23.0 with some sub-module (foo.a) and added the 18.0 version as provided in the "higher level" module (b).
module foo.a
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>23.0</version>
</dependency>
module b
<dependency>
<groupId>foo</groupId>
<artifactId>a</artifactId>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>18.0</version>
<scope>provided</scope>
</dependency>
This way integration tests should identify any clashes, if we manage to have 100% line coverage. BUT unittests would not, see "provided" quote maven:
This scope is only available on the compilation and test classpath, and is not transitive.
meaning unit tests would still use version 18.0

What is the difference between ${spring.version} and literal version number

I saw many tutorial some people use maven dependency such way
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
and some people use maven dependency such way
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>4.3.3.RELEASE</version>
</dependency>
What is the main difference between <version>${spring.version}</version> and <version>4.3.3.RELEASE</version> in maven?

The notation of ${spring.version} is a POM variable. This means that somewhere in POM (or in one of parent POMs), you'll see a definition similar to this:
<spring.version>4.3.3.RELEASE</spring.version>
They both achieve the same end result, but using variables is a bit easier to maintain, especially if you use several artifacts sharing the same version. This way, when you choose to upgrade them, you only need to change the version in one place instead of once per artifact.

What are the Maven coordinates for the JCache API jar?

I have an executable JAR (not a web app being deployed to a standard container like Tomcat, etc.) that needs to connect to a DB and cache a lot of stuff.
If at all possible, I'd like to use the JCache API and inject (via Guice) the Hazelcast implementation. I will code 100% against the JCache API, so that if I ever change my mind and choose another implementation, the swap out should be (relatively) painless.
One problem: where can I get the latest stable JCache JAR?!? (What are the Maven coordinates?)
On Maven Central, all I can find are some dev JARs from 2005! So I ask: where is the JCache?

The jar are available here : javax.cache/cache-api

If you want to use Ehcache implementations, copy/past the dependencies below:
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.12</version>
</dependency>
<dependency>
<groupId>javax.cache</groupId>
<artifactId>cache-api</artifactId>
<version>1.0.0</version>
</dependency>
<dependency>
<groupId>org.ehcache</groupId>
<artifactId>ehcache</artifactId>
<version>3.1.1</version>
<scope>runtime</scope>
</dependency>
Find a complete example here.

How can I update the default version of Spring that Intellij provides?

When I create a Spring project in IntelliJ IDEA, it suggests I use Spring 4.1.6. I want to use 4.2.1 (which I can do after creating the project).
Where can I make the change?
Thanks,
Andy

I don't know if you can change that yourself without an upgrade but you can allow it to create it with that version then manually change it your pom.xml file.
For example,
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>4.2.1.RELEASE</version>
</dependency>
You can also provide a property that an be used on all your Spring dependencies and then you only have to change it one place.
For example,
<properties>
<org.springframework.version>4.2.0.RELEASE</org.springframework.version>
...
</properties>
Then use it like...
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${org.springframework.version}</version>
</dependency>

Do I need to download the dependencies that Spring need in Maven?

I am starting out with Spring and I am reading Pro Spring 2.5. On page 17 they talk about Spring dependencies and I wonder if I need to add this myself in the POM, or does the dependency I have added below do this? Such as CGLib, dom4j etc?
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>3.1.1.RELEASE</version>
</dependency>

You shouldn't need to. Maven will read the pom for spring-context and get any necessary dependencies that it has too, so you won't need to specifically put them in your own pom.
Check out this link it's really handy.

<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>3.1.1.RELEASE</version>
</dependency>
This will just instruct maven that the current POM in which this is declared is dependent on this artfact, so when you compile the app it would make it available for you in classpath