Commands can be parsed, in a very limited way.

src/main/java/net/minecraft/commands/arguments/CommandArgumentType.java

@@ -1,4 +1,7 @@
 package net.minecraft.commands.arguments;
 
-public interface CommandArgumentType {
+import net.minecraft.commands.exceptions.IllegalCommandArgumentException;
+
+public interface CommandArgumentType<T> {
+    T parse(String command) throws IllegalCommandArgumentException;
 }

src/main/java/net/minecraft/commands/arguments/IntegerArgumentType.java

@@ -1,6 +1,8 @@
 package net.minecraft.commands.arguments;
 
-public class IntegerArgumentType implements CommandArgumentType {
+import net.minecraft.commands.exceptions.IllegalCommandArgumentException;
+
+public class IntegerArgumentType implements CommandArgumentType<Integer> {
     private final int minimum;
     private final int maximum;
 
@@ -20,4 +22,22 @@ public class IntegerArgumentType implements CommandArgumentType {
     public static IntegerArgumentType integer(int min, int max) {
         return new IntegerArgumentType(min, max);
     }
+
+    @Override
+    public Integer parse(String command) throws IllegalCommandArgumentException {
+        try {
+            int value = Integer.parseInt(command);
+
+            if (value < minimum) {
+                throw new IllegalCommandArgumentException();
+            }
+            if (value > maximum) {
+                throw new IllegalCommandArgumentException();
+            }
+
+            return value;
+        } catch (NumberFormatException ignored) {
+            throw new IllegalCommandArgumentException();
+        }
+    }
 }

src/main/java/net/minecraft/commands/builder/RequiredArgumentBuilder.java

@@ -3,20 +3,20 @@ package net.minecraft.commands.builder;
 import net.minecraft.commands.arguments.CommandArgumentType;
 import net.minecraft.commands.tree.ArgumentCommandNode;
 
-public class RequiredArgumentBuilder extends ArgumentBuilder {
+public class RequiredArgumentBuilder<T> extends ArgumentBuilder {
     private final String name;
-    private final CommandArgumentType type;
+    private final CommandArgumentType<T> type;
 
-    protected RequiredArgumentBuilder(String name, CommandArgumentType type) {
+    protected RequiredArgumentBuilder(String name, CommandArgumentType<T> type) {
         this.name = name;
         this.type = type;
     }
 
-    public static RequiredArgumentBuilder argument(String name, CommandArgumentType type) {
-        return new RequiredArgumentBuilder(name, type);
+    public static <T> RequiredArgumentBuilder<T> argument(String name, CommandArgumentType<T> type) {
+        return new RequiredArgumentBuilder<T>(name, type);
     }
 
-    public CommandArgumentType getType() {
+    public CommandArgumentType<T> getType() {
         return type;
     }
 
@@ -24,8 +24,8 @@ public class RequiredArgumentBuilder extends ArgumentBuilder {
         return name;
     }
 
-    public ArgumentCommandNode build() {
-        ArgumentCommandNode result = new ArgumentCommandNode(getName(), getType());
+    public ArgumentCommandNode<T> build() {
+        ArgumentCommandNode<T> result = new ArgumentCommandNode<T>(getName(), getType());
 
         for (ArgumentBuilder argument : getArguments()) {
             result.addChild(argument.build());

src/main/java/net/minecraft/commands/exceptions/IllegalCommandArgumentException.java

@@ -0,0 +1,4 @@
+package net.minecraft.commands.exceptions;
+
+public class IllegalCommandArgumentException extends CommandException {
+}

src/main/java/net/minecraft/commands/tree/ArgumentCommandNode.java

@@ -1,12 +1,13 @@
 package net.minecraft.commands.tree;
 
 import net.minecraft.commands.arguments.CommandArgumentType;
+import net.minecraft.commands.exceptions.IllegalCommandArgumentException;
 
-public class ArgumentCommandNode extends CommandNode {
+public class ArgumentCommandNode<T> extends CommandNode {
     private final String name;
-    private final CommandArgumentType type;
+    private final CommandArgumentType<T> type;
 
-    public ArgumentCommandNode(String name, CommandArgumentType type) {
+    public ArgumentCommandNode(String name, CommandArgumentType<T> type) {
         this.name = name;
         this.type = type;
     }
@@ -15,7 +16,12 @@ public class ArgumentCommandNode extends CommandNode {
         return name;
     }
 
-    public CommandArgumentType getType() {
+    public CommandArgumentType<T> getType() {
         return type;
     }
+
+    @Override
+    public void parse(String command) throws IllegalCommandArgumentException {
+        type.parse(command);
+    }
 }

src/main/java/net/minecraft/commands/tree/CommandNode.java

@@ -1,6 +1,7 @@
 package net.minecraft.commands.tree;
 
 import com.google.common.collect.Lists;
+import net.minecraft.commands.exceptions.IllegalCommandArgumentException;
 
 import java.util.List;
 
@@ -14,4 +15,6 @@ public abstract class CommandNode {
     public void addChild(CommandNode node) {
         children.add(node);
     }
+
+    public abstract void parse(String command) throws IllegalCommandArgumentException;
 }

src/main/java/net/minecraft/commands/tree/LiteralCommandNode.java

@@ -1,5 +1,7 @@
 package net.minecraft.commands.tree;
 
+import net.minecraft.commands.exceptions.IllegalCommandArgumentException;
+
 public class LiteralCommandNode extends CommandNode {
     private final String literal;
     private final Runnable executor;
@@ -16,4 +18,11 @@ public class LiteralCommandNode extends CommandNode {
     public Runnable getExecutor() {
         return executor;
     }
+
+    @Override
+    public void parse(String command) throws IllegalCommandArgumentException {
+        if (!command.equals(literal)) {
+            throw new IllegalCommandArgumentException();
+        }
+    }
 }

src/main/test/net/minecraft/commands/arguments/IntegerArgumentTypeTest.java

@@ -0,0 +1,48 @@
+package net.minecraft.commands.arguments;
+
+import net.minecraft.commands.exceptions.IllegalCommandArgumentException;
+import org.junit.Before;
+import org.junit.Test;
+
+import static net.minecraft.commands.arguments.IntegerArgumentType.integer;
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+public class IntegerArgumentTypeTest {
+    IntegerArgumentType type;
+
+    @Before
+    public void setUp() throws Exception {
+        type = integer(-100, 100);
+    }
+
+    @Test
+    public void testParse() throws Exception {
+        assertThat(type.parse("50"), is(50));
+    }
+
+    @Test(expected = IllegalCommandArgumentException.class)
+    public void testParseInvalid() throws Exception {
+        type.parse("fifty");
+    }
+
+    @Test(expected = IllegalCommandArgumentException.class)
+    public void testParseTooLow() throws Exception {
+        type.parse("-101");
+    }
+
+    @Test
+    public void testParseLowerLimit() throws Exception {
+        assertThat(type.parse("-100"), is(-100));
+    }
+
+    @Test(expected = IllegalCommandArgumentException.class)
+    public void testParseTooHigh() throws Exception {
+        type.parse("101");
+    }
+
+    @Test
+    public void testParseHigherLimit() throws Exception {
+        assertThat(type.parse("100"), is(100));
+    }
+}

src/main/test/net/minecraft/commands/builder/RequiredArgumentBuilderTest.java

@@ -13,8 +13,8 @@ import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertThat;
 
 public class RequiredArgumentBuilderTest {
-    @Mock CommandArgumentType type;
-    RequiredArgumentBuilder builder;
+    @Mock CommandArgumentType<Integer> type;
+    RequiredArgumentBuilder<Integer> builder;
 
     @Before
     public void setUp() throws Exception {
@@ -23,7 +23,7 @@ public class RequiredArgumentBuilderTest {
 
     @Test
     public void testBuild() throws Exception {
-        ArgumentCommandNode node = builder.build();
+        ArgumentCommandNode<Integer> node = builder.build();
 
         assertThat(node.getName(), is("foo"));
         assertThat(node.getType(), is(type));

src/main/test/net/minecraft/commands/tree/ArgumentCommandNodeTest.java

@@ -0,0 +1,27 @@
+package net.minecraft.commands.tree;
+
+import net.minecraft.commands.exceptions.IllegalCommandArgumentException;
+import org.junit.Before;
+import org.junit.Test;
+
+import static net.minecraft.commands.arguments.IntegerArgumentType.integer;
+import static net.minecraft.commands.builder.RequiredArgumentBuilder.argument;
+
+public class ArgumentCommandNodeTest {
+    ArgumentCommandNode node;
+
+    @Before
+    public void setUp() throws Exception {
+        node = argument("foo", integer()).build();
+    }
+
+    @Test
+    public void testParse() throws Exception {
+        node.parse("123");
+    }
+
+    @Test(expected = IllegalCommandArgumentException.class)
+    public void testParseInvalid() throws Exception {
+        node.parse("bar");
+    }
+}

src/main/test/net/minecraft/commands/tree/LiteralCommandNodeTest.java

@@ -0,0 +1,26 @@
+package net.minecraft.commands.tree;
+
+import net.minecraft.commands.exceptions.IllegalCommandArgumentException;
+import org.junit.Before;
+import org.junit.Test;
+
+import static net.minecraft.commands.builder.CommandBuilder.command;
+
+public class LiteralCommandNodeTest {
+    LiteralCommandNode node;
+
+    @Before
+    public void setUp() throws Exception {
+        node = command("foo").build();
+    }
+
+    @Test
+    public void testParse() throws Exception {
+        node.parse("foo");
+    }
+
+    @Test(expected = IllegalCommandArgumentException.class)
+    public void testParseInvalid() throws Exception {
+        node.parse("bar");
+    }
+}