Merge pull request #290 from CDsigma/javaVerlet

Implementation Edit to Verlet Integration in Java

Author: Gathros

contents/verlet_integration/code/java/Verlet.java

@@ -0,0 +1,80 @@
+// Submitted by lolatomroflsinnlos
+public class VerletValues {
+	public double time;
+	public double vel;
+  
+	public VerletValues(double time, double vel) {
+        this.time = time;
+        this.vel = vel;
+    }
+}
+
+public class Verlet {
+    static double verlet(double pos, double acc, double dt) {
+
+      // Note that we are using a temp variable for the previous position
+      double prev_pos, temp_pos, time;
+      prev_pos = pos;
+      time = 0;
+
+      while (pos > 0) {
+            time += dt;
+            temp_pos = pos;
+            pos = pos*2 - prev_pos + acc * dt * dt;
+            prev_pos = temp_pos;
+        }
+
+        return time;
+    }
+  
+    static VerletValues stormer_verlet(double pos, double acc, double dt) {
+
+        // Note that we are using a temp variable for the previous position
+        double prev_pos, temp_pos, time, vel;
+        prev_pos = pos;
+        vel = 0;
+        time = 0;
+        while (pos > 0) {
+            time += dt;
+            temp_pos = pos;
+            pos = pos*2 - prev_pos + acc * dt * dt;
+            prev_pos = temp_pos;
+
+            // The acceleration is constant, so the velocity is straightforward
+             vel += acc*dt;
+        }
+      
+       VerletValues stormerVerlet = new VerletValues(time, vel);
+       return stormerVerlet;
+    }
+
+    static VerletValues velocity_verlet(double pos, double acc, double dt) {
+
+        // Note that we are using a temp variable for the previous position
+        double time, vel;
+        vel = 0;
+        time = 0;
+        while (pos > 0) {
+            time += dt;
+            pos += vel*dt + 0.5*acc * dt * dt;
+            vel += acc*dt;
+      }
+
+        VerletValues velocityVerlet = new VerletValues(time, vel);
+        return velocityVerlet;
+    }
+
+    public static void main(String[] args) {
+
+        double verletTime = verlet(5.0, -10, 0.01);
+        System.out.println("Time for Verlet integration is: " + verletTime);
+      
+        VerletValues stormerVerlet = stormer_verlet(5.0, -10, 0.01);
+        System.out.println("Time for Stormer Verlet integration is: " + stormerVerlet.time);
+        System.out.println("Velocity for Stormer Verlet integration is: " + stormerVerlet.vel);
+        
+        VerletValues velocityVerlet = velocity_verlet(5.0, -10, 0.01);
+        System.out.println("Time for velocity Verlet integration is: " + velocityVerlet.time);
+        System.out.println("Velocity for velocity Verlet integration is: " + velocityVerlet.vel);
+    }
+}

contents/verlet_integration/code/java/verlet.java

@@ -37,7 +37,7 @@ Here is what it looks like in code:
 {% sample lang="c" %}
 [import:3-14, lang:"c_cpp"](code/c/verlet.c)
 {% sample lang="java" %}
-[import:2-18, lang:"java"](code/java/verlet.java)
+[import:13-28, lang:"java"](code/java/Verlet.java)
 {% sample lang="py" %}
 [import:1-9, lang:"python"](code/python/verlet.py)
 {% sample lang="hs" %}
@@ -82,7 +82,7 @@ However, the error for this is $$\mathcal{O}(\Delta t)$$, which is quite poor, b
 {% sample lang="c" %}
 [import:16-31, lang:"c_cpp"](code/c/verlet.c)
 {% sample lang="java" %}
-[import:21-40, lang:"java"](code/java/verlet.java)
+[import:30-49, lang:"java"](code/java/Verlet.java)
 {% sample lang="py" %}
 [import:11-21, lang:"python"](code/python/verlet.py)
 {% sample lang="hs" %}
@@ -141,7 +141,7 @@ Here is the velocity Verlet method in code:
 {% sample lang="c" %}
 [import:33-43, lang:"c_cpp"](code/c/verlet.c)
 {% sample lang="java" %}
-[import:43-57, lang:"java"](code/java/verlet.java)
+[import:51-65, lang:"java"](code/java/Verlet.java)
 {% sample lang="py" %}
 [import:23-32, lang:"python"](code/python/verlet.py)
 {% sample lang="hs" %}
@@ -178,7 +178,7 @@ Both of these methods work simply by iterating timestep-by-timestep and can be w
 {% sample lang="c" %}
 [import, lang:"c_cpp"](code/c/verlet.c)
 {% sample lang="java" %}
-[import, lang:"java"](code/java/verlet.java)
+[import, lang:"java"](code/java/Verlet.java)
 {% sample lang="py" %}
 [import, lang:"python"](code/python/verlet.py)
 {% sample lang="hs" %}