[JENKINS-44851] Agents JVM must be 1.8+ now (#2915)

* [JENKINS-44851] Agents JVM must be 1.8+ now

* [JENKINS-44851] Fix tests

* Fix old Java 6 and 7 tests (an exception is expected now)
* Add new tests to Java 8
* Fix messages

core/src/main/java/hudson/slaves/ComputerLauncher.java

@@ -187,7 +187,7 @@ public abstract class ComputerLauncher extends AbstractDescribableImpl<ComputerL
                 final String versionStr = m.group(1);
                 logger.println(Messages.ComputerLauncher_JavaVersionResult(javaCommand, versionStr));
                 try {
-                    if (new DeweyDecimal(versionStr).isLessThan(new DeweyDecimal("1.6"))) {
+                    if (new DeweyDecimal(versionStr).isLessThan(new DeweyDecimal("1.8"))) {
                         throw new IOException(Messages
                                 .ComputerLauncher_NoJavaFound(line));
                     }

core/src/main/resources/hudson/slaves/Messages.properties

@@ -36,7 +36,7 @@ SimpleScheduledRetentionStrategy.displayName=Take this agent online according to
 EnvironmentVariablesNodeProperty.displayName=Environment variables
 SlaveComputer.DisconnectedBy=Disconnected by {0}{1}
 NodeDescriptor.CheckName.Mandatory=Name is mandatory
-ComputerLauncher.NoJavaFound=Java version {0} was found but 1.6 or later is needed.
+ComputerLauncher.NoJavaFound=Java version {0} was found but 1.8 or later is needed.
 ComputerLauncher.JavaVersionResult={0} -version returned {1}.
 ComputerLauncher.UnknownJavaVersion=Couldn\u2019t figure out the Java version of {0}
 Cloud.ProvisionPermission.Description=Provision new nodes

core/src/test/java/hudson/slaves/ComputerLauncherTest.java

@@ -36,15 +36,15 @@ import static org.junit.Assert.*;
 
 public class ComputerLauncherTest {
 
-    @Test public void jdk7() throws IOException {
+    @Test(expected=IOException.class) public void jdk7() throws IOException {
         assertChecked("java version \"1.7.0_05\"\nJava(TM) SE Runtime Environment (build 1.7.0_05-b05)\nJava HotSpot(TM) Server VM (build 23.1-b03, mixed mode)\n", "1.7.0");
     }
 
-    @Test public void openJDK7() throws IOException {
+    @Test(expected=IOException.class) public void openJDK7() throws IOException {
         assertChecked("openjdk version \"1.7.0-internal\"\nOpenJDK Runtime Environment (build 1.7.0-internal-pkgsrc_2010_01_03_06_54-b00)\nOpenJDK 64-Bit Server VM (build 17.0-b04, mixed mode)\n", "1.7.0");
     }
 
-    @Test public void jdk6() throws IOException {
+    @Test(expected=IOException.class) public void jdk6() throws IOException {
         assertChecked("java version \"1.6.0_33\"\nJava(TM) SE Runtime Environment (build 1.6.0_33-b03)\nJava HotSpot(TM) Server VM (build 20.8-b03, mixed mode)\n", "1.6.0");
     }
 
@@ -56,6 +56,14 @@ public class ComputerLauncherTest {
         ComputerLauncher.checkJavaVersion(new PrintStream(new NullOutputStream()), "-", new BufferedReader(new StringReader("java version \"1.4.2_19\"\nJava(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_19-b04)\nJava HotSpot(TM) Client VM (build 1.4.2_19-b04, mixed mode)\n")));
     }
 
+    @Test public void jdk8() throws IOException {
+        assertChecked("java version \"1.8.0_05\"\nJava(TM) SE Runtime Environment (build 1.8.0_05-b05)\nJava HotSpot(TM) Server VM (build 23.1-b03, mixed mode)\n", "1.8.0");
+    }
+
+    @Test public void openJDK8() throws IOException {
+        assertChecked("openjdk version \"1.8.0-internal\"\nOpenJDK Runtime Environment (build 1.8.0-internal-pkgsrc_2015_01_03_06_54-b00)\nOpenJDK 64-Bit Server VM (build 17.0-b04, mixed mode)\n", "1.8.0");
+    }
+
     @Test public void jdk10() throws IOException { // predicted
         assertChecked("java version \"1.10.0_02\"\nJava(TM) SE Runtime Environment (build 1.10.0_02-b01)\nJava HotSpot(TM) Server VM (build 23.1-b03, mixed mode)\n", "1.10.0");
     }