solved ex3

src/main/java/ch/zhaw/ads/BracketServer.java

@@ -0,0 +1,48 @@
+package ch.zhaw.ads;
+
+import java.util.Map;
+import static java.util.Map.entry;    
+
+public class BracketServer implements CommandExecutor {
+
+    @Override
+    public String execute(String command) {
+        StringBuffer result = new StringBuffer(100);
+        result.append("Die Eingabe war \"");
+        result.append(command);
+        result.append("\"\n");
+        return result.toString();
+    }
+
+    private Map<Character, Character> openingBrackets = Map.ofEntries(
+            entry('(', ')'),
+            entry('[', ']'),
+            entry('{', '}')
+            );
+
+    private Map<Character, Character> closingBrackets = Map.ofEntries(
+            entry(')', '('),
+            entry(']', '['),
+            entry('}', '{')
+            );
+
+    public boolean checkBrackets(String input) {
+        ListStack<Character> bracketStack = new ListStack<>();
+        for (int i = 0; i < input.length(); i++) {
+            char cur_char = input.charAt(i);
+            if (openingBrackets.containsKey(cur_char)) {
+                bracketStack.push(cur_char);
+            }
+            if (closingBrackets.containsKey(cur_char)) {
+                if (bracketStack.isEmpty()) {
+                    return false;
+                }
+                Character last = (Character) bracketStack.pop();
+                if (last != closingBrackets.get(cur_char)) {
+                    return false;
+                }
+            }
+        }
+        return bracketStack.isEmpty();
+    }
+}

src/test/java/ch/zhaw/ads/BracketServerTest.java

@@ -3,9 +3,10 @@ package ch.zhaw.ads;
 import org.junit.Test;
 import org.junit.Before;
 import static org.junit.Assert.*;
+
 public class BracketServerTest {
 	
-/*	BracketServer bs;
+	BracketServer bs;
 	
 	@Before
 	public void setUp() throws Exception {
@@ -24,6 +25,4 @@ public class BracketServerTest {
 		test("[(3 +3)* 35 +3]* {3 +2}",true);
 		test("[({3 +3)* 35} +3]* {3 +2}",false);
 	}
-
-	*/
 }