From ac29ae34a15ff7dbabe295e94033bf5eff9d0d6d Mon Sep 17 00:00:00 2001
From: Joe Klonowski <Joe_Klonowski@intuit.com>
Date: Wed, 17 Oct 2018 10:23:00 -0700
Subject: [PATCH 1/4] Add Java implementation of Forward Euler

---
 .../forward_euler_method/code/java/Euler.java | 38 +++++++++++++++++++
 .../forward_euler_method.md                   |  2 +
 2 files changed, 40 insertions(+)
 create mode 100644 contents/forward_euler_method/code/java/Euler.java

diff --git a/contents/forward_euler_method/code/java/Euler.java b/contents/forward_euler_method/code/java/Euler.java
new file mode 100644
index 000000000..ad0e1ad92
--- /dev/null
+++ b/contents/forward_euler_method/code/java/Euler.java
@@ -0,0 +1,38 @@
+public class Euler {
+    private static double[] solveEuler(double timestep, int n) {
+        double[] eulerResult = new double[n];
+
+        //Setting the initial condition
+        eulerResult[1] = 1;
+        for(int i = 2; i < eulerResult.length; i++) {
+            eulerResult[i] = eulerResult[i-1] - (3 * eulerResult[i-1] * timestep);
+        }
+        return eulerResult;
+    }
+
+    private static boolean checkResult(double[] eulerResult, double threshold, double timestep) {
+        boolean isApprox = true;
+
+        for(int i = 1; i < eulerResult.length; i++) {
+            double time = (i - 1) * timestep;
+            double solution = Math.exp(-3*time);
+            if(Math.abs(eulerResult[i] - solution) > threshold) {
+                System.out.println(eulerResult[i] + " " + solution);
+                isApprox = false;
+            }
+        }
+
+        return isApprox;
+    }
+
+    public static void main(String[] args) {
+        double timestep = 0.1;
+        int n = 100;
+        double threshold = 0.1;
+
+        double[] eulerResult = solveEuler(timestep, n);
+        boolean isApprox = checkResult(eulerResult, threshold, timestep);
+
+        System.out.println(isApprox);
+    }
+}
diff --git a/contents/forward_euler_method/forward_euler_method.md b/contents/forward_euler_method/forward_euler_method.md
index 5ed5425fb..3bf4e5c2c 100644
--- a/contents/forward_euler_method/forward_euler_method.md
+++ b/contents/forward_euler_method/forward_euler_method.md
@@ -128,6 +128,8 @@ Full code for the visualization follows:
 [import, lang:"go"](code/golang/euler.go)
 {% sample lang="asm-x64" %}
 [import, lang:"asm-x64"](code/asm-x64/euler.s)
+{% sample lang="java" %}
+[import, lang:"java"](code/java/euler.java)
 {% endmethod %}
 
 <script>

From 8e9f7eff9e56700d85a7cae97dd8c387eef7b00e Mon Sep 17 00:00:00 2001
From: Joe Klonowski <Joe_Klonowski@intuit.com>
Date: Wed, 17 Oct 2018 17:45:37 -0700
Subject: [PATCH 2/4] Style and indexing fixes

---
 .../code/java/{Euler.java => ForwardEuler.java}      | 12 ++++++------
 .../forward_euler_method/forward_euler_method.md     |  2 +-
 2 files changed, 7 insertions(+), 7 deletions(-)
 rename contents/forward_euler_method/code/java/{Euler.java => ForwardEuler.java} (79%)

diff --git a/contents/forward_euler_method/code/java/Euler.java b/contents/forward_euler_method/code/java/ForwardEuler.java
similarity index 79%
rename from contents/forward_euler_method/code/java/Euler.java
rename to contents/forward_euler_method/code/java/ForwardEuler.java
index ad0e1ad92..caa55263d 100644
--- a/contents/forward_euler_method/code/java/Euler.java
+++ b/contents/forward_euler_method/code/java/ForwardEuler.java
@@ -1,11 +1,11 @@
-public class Euler {
+public class ForwardEuler {
     private static double[] solveEuler(double timestep, int n) {
         double[] eulerResult = new double[n];
 
         //Setting the initial condition
-        eulerResult[1] = 1;
-        for(int i = 2; i < eulerResult.length; i++) {
-            eulerResult[i] = eulerResult[i-1] - (3 * eulerResult[i-1] * timestep);
+        eulerResult[0] = 1;
+        for(int i = 1; i < eulerResult.length; i++) {
+            eulerResult[i] = eulerResult[i - 1] - (3 * eulerResult[i - 1] * timestep);
         }
         return eulerResult;
     }
@@ -13,9 +13,9 @@ private static double[] solveEuler(double timestep, int n) {
     private static boolean checkResult(double[] eulerResult, double threshold, double timestep) {
         boolean isApprox = true;
 
-        for(int i = 1; i < eulerResult.length; i++) {
+        for(int i = 0; i < eulerResult.length; i++) {
             double time = (i - 1) * timestep;
-            double solution = Math.exp(-3*time);
+            double solution = Math.exp(-3 * time);
             if(Math.abs(eulerResult[i] - solution) > threshold) {
                 System.out.println(eulerResult[i] + " " + solution);
                 isApprox = false;
diff --git a/contents/forward_euler_method/forward_euler_method.md b/contents/forward_euler_method/forward_euler_method.md
index 3bf4e5c2c..6016fdb79 100644
--- a/contents/forward_euler_method/forward_euler_method.md
+++ b/contents/forward_euler_method/forward_euler_method.md
@@ -129,7 +129,7 @@ Full code for the visualization follows:
 {% sample lang="asm-x64" %}
 [import, lang:"asm-x64"](code/asm-x64/euler.s)
 {% sample lang="java" %}
-[import, lang:"java"](code/java/euler.java)
+[import, lang:"java"](code/java/ForwardEuler.java)
 {% endmethod %}
 
 <script>

From a66a9d2879f64ad3c316b548d77b134ba5e0f601 Mon Sep 17 00:00:00 2001
From: Atocil <klonowskijoseph@gmail.com>
Date: Mon, 22 Oct 2018 11:55:09 -0700
Subject: [PATCH 3/4] Correct (hopefully) last indexing error

---
 contents/forward_euler_method/code/java/ForwardEuler.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contents/forward_euler_method/code/java/ForwardEuler.java b/contents/forward_euler_method/code/java/ForwardEuler.java
index caa55263d..a65db2a92 100644
--- a/contents/forward_euler_method/code/java/ForwardEuler.java
+++ b/contents/forward_euler_method/code/java/ForwardEuler.java
@@ -14,7 +14,7 @@ private static boolean checkResult(double[] eulerResult, double threshold, doubl
         boolean isApprox = true;
 
         for(int i = 0; i < eulerResult.length; i++) {
-            double time = (i - 1) * timestep;
+            double time = (i) * timestep;
             double solution = Math.exp(-3 * time);
             if(Math.abs(eulerResult[i] - solution) > threshold) {
                 System.out.println(eulerResult[i] + " " + solution);

From 857d480a700f75fd293eb800aebcc99ec04d9011 Mon Sep 17 00:00:00 2001
From: Atocil <klonowskijoseph@gmail.com>
Date: Mon, 22 Oct 2018 13:39:25 -0700
Subject: [PATCH 4/4] Formatting

---
 contents/forward_euler_method/code/java/ForwardEuler.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contents/forward_euler_method/code/java/ForwardEuler.java b/contents/forward_euler_method/code/java/ForwardEuler.java
index a65db2a92..16d398a5f 100644
--- a/contents/forward_euler_method/code/java/ForwardEuler.java
+++ b/contents/forward_euler_method/code/java/ForwardEuler.java
@@ -14,7 +14,7 @@ private static boolean checkResult(double[] eulerResult, double threshold, doubl
         boolean isApprox = true;
 
         for(int i = 0; i < eulerResult.length; i++) {
-            double time = (i) * timestep;
+            double time = i * timestep;
             double solution = Math.exp(-3 * time);
             if(Math.abs(eulerResult[i] - solution) > threshold) {
                 System.out.println(eulerResult[i] + " " + solution);