Implement the components of a new tree builder.

src/org/nwapw/abacus/parsing/Parser.java

@@ -0,0 +1,10 @@
+package org.nwapw.abacus.parsing;
+
+import org.nwapw.abacus.tree.TreeNode;
+
+import java.util.List;
+
+public interface Parser<T> {
+
+    public TreeNode constructTree(List<T> tokens);
+}

src/org/nwapw/abacus/parsing/Tokenizer.java

@@ -0,0 +1,9 @@
+package org.nwapw.abacus.parsing;
+
+import java.util.List;
+
+public interface Tokenizer<T> {
+
+    public List<T> tokenizeString(String string);
+
+}

src/org/nwapw/abacus/parsing/TreeBuilder.java

@@ -0,0 +1,23 @@
+package org.nwapw.abacus.parsing;
+
+import org.nwapw.abacus.tree.TreeNode;
+
+import java.util.List;
+
+public class TreeBuilder<T> {
+
+    private Tokenizer<T> tokenizer;
+    private Parser<T> parser;
+
+    public TreeBuilder(Tokenizer<T> tokenizer, Parser<T> parser){
+        this.tokenizer = tokenizer;
+        this.parser = parser;
+    }
+
+    public TreeNode fromString(String input){
+        List<T> tokens = tokenizer.tokenizeString(input);
+        if(tokens == null) return null;
+        return parser.constructTree(tokens);
+    }
+
+}