first commit

Author: mvpjava

README

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+when you run.sh the container will run the demo in jshell
+===========================================================
+to re-execute it while in jshell..
+
+jshell> /open /root/jdkSwitchDemo.jsh
+==========================================================
+When you want to list the code snippets in jshell script
+jshell> /list
+
+   1 : System.out.println("MVP Java - JDK 12 Switch Demo")
+   2 : import java.time.DayOfWeek;
+   3 : DayOfWeek day = DayOfWeek.MONDAY;
+   4 : switch (day) {
+           case MONDAY, FRIDAY, SUNDAY -> System.out.println(6);
+           case TUESDAY                -> System.out.println(7);
+           case THURSDAY, SATURDAY     -> System.out.println(8);
+           case WEDNESDAY              -> System.out.println(9);
+       }
+
+then you can /list 1
+for individual snippets

jdk12SwitchDemoNew.jsh

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+System.out.println("MVP Java - JDK 12 Switch Demo - New")
+
+public enum SYSTEM {
+    POWER, ACS, THERMAL, COMS
+}
+
+public double calculatePowerUsgae(SYSTEM system)
+{
+	double power =  switch (system) 
+    {
+	     case POWER ->  200.0D;
+	     case ACS   ->  {
+							//i.e: Sum Power Usage from all Actuators
+							double yesThisIsReallyLocalScope = 10 + 20 + 30;							
+							break yesThisIsReallyLocalScope;
+						}
+	     case THERMAL, COMS -> 110.0D;
+	};
+
+	return power;
+}
+
+SYSTEM acs = SYSTEM.ACS;
+
+System.out.printf ("Attitude Control System (ACS) taking %.3f mW of Power", 
+					calculatePowerUsgae(acs))

jdk12SwitchDemoNew_Exhaustiveness.jsh

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+System.out.println("MVP Java - JDK 12 Switch Demo - New Exhaustive")
+
+public enum SYSTEM {
+    POWER, ACS, THERMAL, COMS, PAYLOAD
+}
+
+public double calculatePowerUsgae(SYSTEM system)
+{
+	double power = switch (system) 
+    {
+     case POWER ->  200;
+     case ACS   ->  140;
+     case THERMAL, COMS -> 110;
+	//  Compile Error: the switch expression does not cover all possible input values
+    //case PAYLOAD -> 342.67;
+	};
+
+	return power;
+}
+
+SYSTEM acs = SYSTEM.ACS;
+
+System.out.printf ("Attitude Control System (ACS) taking %.3f mW of Power", calculatePowerUsgae(acs))

jdk12SwitchDemoOriginalExpression.jsh

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+System.out.println("MVP Java - JDK 12 Switch Demo - Original")
+
+public enum SYSTEM {
+    POWER, ACS, THERMAL, COMS
+}
+
+public double calculatePowerUsgae(SYSTEM system)
+{
+	double power = switch (system) {
+		 case POWER:
+           double thisReallyIsGlobalScope = 10 * 20;
+		   break 200 + thisReallyIsGlobalScope;
+		   //break; compile error: missing break value
+
+		 case ACS:
+           thisReallyIsGlobalScope = 1;
+		   break 140 + thisReallyIsGlobalScope;
+
+		 case THERMAL: case COMS:
+		   break 110;
+
+		 default:
+		   throw new RuntimeException("Invalid Sub-System <" + system + "> encountered");
+	};
+	 
+	return power;
+}
+
+SYSTEM acs = SYSTEM.ACS
+
+System.out.printf ("Attitude Control System (ACS) taking %.3f mW of Power", calculatePowerUsgae(acs))
+
+

run.sh

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+docker run --rm -it -v $PWD:/root openjdk:12-jdk-oracle jshell --enable-preview  /root/switchDemoOriginal.jsh
+

switchDemoOriginal.jsh

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+System.out.println("MVP Java - JDK 12 Switch Demo - Original")
+
+public enum SYSTEM {
+    POWER, ACS, THERMAL, COMS
+}
+
+public double calculatePowerUsgae(SYSTEM system)
+{
+	double power = 0;
+
+	switch (system) {
+		 case POWER:
+           double thisReallyIsGlobalScope = 10 * 20;
+		   power = 200 + thisReallyIsGlobalScope;
+		   break;
+
+		 case ACS:
+           thisReallyIsGlobalScope = 1;
+		   power = 140 + thisReallyIsGlobalScope;
+		   break;
+
+		 case THERMAL: case COMS:
+		   power = 110;
+		   break;
+
+		 default:
+		   System.out.println ("Invalid Sub-System <" + system + "> encountered");
+		   break;
+	}
+	 
+	return power;
+}
+
+
+SYSTEM acs = SYSTEM.ACS
+
+System.out.printf ("Attitude Control System (ACS) taking %.3f mW of Power", calculatePowerUsgae(acs))
+
+