diff --git a/pdl-compiler/src/backends/java/codegen/packet.rs b/pdl-compiler/src/backends/java/codegen/packet.rs
index 3b0bf6e..3ea5d7d 100644
--- a/pdl-compiler/src/backends/java/codegen/packet.rs
+++ b/pdl-compiler/src/backends/java/codegen/packet.rs
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use std::collections::HashMap;
+use std::collections::{BTreeMap, HashMap};
 
 use genco::{self, prelude::Java, quote, tokens::quoted, Tokens};
 use heck::{self, ToLowerCamelCase, ToUpperCamelCase};
@@ -142,7 +142,7 @@ pub fn gen_packet(name: &String, def: &PacketDef, ctx: &Context) -> Tokens<Java>
 
                 $(setter_defs(
                     &def.members, &quote!(Builder),
-                    &HashMap::new(), &def.width_fields, &ctx.heirarchy))
+                    &BTreeMap::new(), &def.width_fields, &ctx.heirarchy))
             }
         }
     }
@@ -266,7 +266,7 @@ pub fn gen_abstract_packet(
             }
 
             protected abstract static class UnconstrainedBuilder<B extends Builder<B>> extends Builder<B> {
-                $(setter_defs(&def.members, &quote!(B), &HashMap::new(), &def.width_fields, &ctx.heirarchy))
+                $(setter_defs(&def.members, &quote!(B), &BTreeMap::new(), &def.width_fields, &ctx.heirarchy))
             }
 
             $(for child in children.iter() {
@@ -319,7 +319,7 @@ fn getter_defs(members: &[Field]) -> Tokens<Java> {
 fn setter_defs(
     members: &[Field],
     builder_type: &Tokens<Java>,
-    constraints: &HashMap<String, Constraint>,
+    constraints: &BTreeMap<String, Constraint>,
     width_fields: &HashMap<String, WidthField>,
     heirarchy: &ClassHeirarchy,
 ) -> Tokens<Java> {
diff --git a/pdl-compiler/src/backends/java/inheritance.rs b/pdl-compiler/src/backends/java/inheritance.rs
index 1d244f6..761a911 100644
--- a/pdl-compiler/src/backends/java/inheritance.rs
+++ b/pdl-compiler/src/backends/java/inheritance.rs
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use std::collections::{HashMap, HashSet};
+use std::collections::{BTreeMap, HashMap, HashSet};
 
 use crate::backends::java::Field;
 
@@ -27,7 +27,7 @@ pub struct InheritanceNode {
     pub name: String,
     pub parent: Option<String>,
     pub children: Vec<String>,
-    pub constraints: HashMap<String, Constraint>,
+    pub constraints: BTreeMap<String, Constraint>,
     pub static_field_width: usize,
     pub dyn_fields: HashSet<String>,
 }
@@ -64,7 +64,7 @@ impl ClassHeirarchy {
                 name,
                 parent: None,
                 children: Vec::new(),
-                constraints: HashMap::new(),
+                constraints: BTreeMap::new(),
                 static_field_width,
                 dyn_fields: non_static_members,
             },
@@ -75,7 +75,7 @@ impl ClassHeirarchy {
         &mut self,
         parent_name: String,
         child_name: String,
-        constraints: HashMap<String, Constraint>,
+        constraints: BTreeMap<String, Constraint>,
         fields: &Vec<Field>,
     ) {
         self.0
diff --git a/pdl-compiler/src/backends/java/mod.rs b/pdl-compiler/src/backends/java/mod.rs
index d54ab58..053ceef 100644
--- a/pdl-compiler/src/backends/java/mod.rs
+++ b/pdl-compiler/src/backends/java/mod.rs
@@ -21,6 +21,7 @@ use genco::{
 use heck::{self, ToLowerCamelCase, ToUpperCamelCase};
 use std::{
     cmp,
+    collections::BTreeMap,
     collections::HashMap,
     fs::{self, OpenOptions},
     iter, mem,
@@ -137,7 +138,7 @@ fn generate_classes(file: &ast::File) -> (HashMap<String, Class>, ClassHeirarchy
                     heirarchy.add_child(
                         parent_name.clone(),
                         child_name.clone(),
-                        HashMap::new(),
+                        BTreeMap::new(),
                         child.fields().unwrap(),
                     );