diff --git a/src/main/java/cn/maxpixel/mcdecompiler/asm/ClassifiedMappingRemapper.java b/src/main/java/cn/maxpixel/mcdecompiler/asm/ClassifiedMappingRemapper.java
index 5d7aa3f..7ec3f08 100644
--- a/src/main/java/cn/maxpixel/mcdecompiler/asm/ClassifiedMappingRemapper.java
+++ b/src/main/java/cn/maxpixel/mcdecompiler/asm/ClassifiedMappingRemapper.java
@@ -254,12 +254,14 @@ private Optional<PairedMapping> processSuperField(String owner, String name) {
     }
 
     private PairedMapping reduceField(PairedMapping left, PairedMapping right) {
+        if (left == right) return left;
         int leftAcc = extraClassesInformation.getAccessFlags(left.getOwned().owner.mapping.unmappedName,
                 left.unmappedName) & (Opcodes.ACC_PUBLIC | Opcodes.ACC_PROTECTED | Opcodes.ACC_PRIVATE);
         int rightAcc = extraClassesInformation.getAccessFlags(right.getOwned().owner.mapping.unmappedName,
                 right.unmappedName) & (Opcodes.ACC_PUBLIC | Opcodes.ACC_PROTECTED | Opcodes.ACC_PRIVATE);
         if((leftAcc & (Opcodes.ACC_PUBLIC | Opcodes.ACC_PROTECTED)) != 0) {
-            if((rightAcc & (Opcodes.ACC_PUBLIC | Opcodes.ACC_PROTECTED)) != 0) throw new IllegalArgumentException("This can't happen!");
+            if((rightAcc & (Opcodes.ACC_PUBLIC | Opcodes.ACC_PROTECTED)) != 0)
+                throw new IllegalArgumentException("This can't happen!");
             return left;
         } else if((rightAcc & (Opcodes.ACC_PUBLIC | Opcodes.ACC_PROTECTED)) != 0) return right;
         else if(Modifier.isPrivate(leftAcc) || Modifier.isPrivate(rightAcc))
diff --git a/src/main/java/cn/maxpixel/mcdecompiler/mapping/collection/ClassMapping.java b/src/main/java/cn/maxpixel/mcdecompiler/mapping/collection/ClassMapping.java
index 6e90ce8..c43ccba 100644
--- a/src/main/java/cn/maxpixel/mcdecompiler/mapping/collection/ClassMapping.java
+++ b/src/main/java/cn/maxpixel/mcdecompiler/mapping/collection/ClassMapping.java
@@ -256,8 +256,7 @@ public static void setMappedNamespace(ClassMapping<? extends NameGetter.Namespac
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;
-        if (!(o instanceof ClassMapping)) return false;
-        ClassMapping<?> that = (ClassMapping<?>) o;
+        if (!(o instanceof ClassMapping<?> that)) return false;
         return mapping.equals(that.mapping) && methods.equals(that.methods) && fields.equals(that.fields);
     }
 
diff --git a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Descriptor.java b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Descriptor.java
index 103a501..eddbcfe 100644
--- a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Descriptor.java
+++ b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Descriptor.java
@@ -22,6 +22,8 @@
 import org.intellij.lang.annotations.Subst;
 import org.jetbrains.annotations.NotNull;
 
+import java.util.Objects;
+
 /**
  * Descriptor component for paired mappings
  */
@@ -30,7 +32,7 @@ public class Descriptor implements Component {
     public @NotNull String unmappedDescriptor;
 
     public Descriptor(@NotNull String unmappedDescriptor) {
-        this.unmappedDescriptor = unmappedDescriptor;
+        this.unmappedDescriptor = Objects.requireNonNull(unmappedDescriptor);
     }
 
     public void reverseUnmapped(ClassifiedMappingRemapper remapper) {
@@ -42,7 +44,7 @@ public void reverseUnmapped(ClassifiedMappingRemapper remapper) {
     }
 
     public void setUnmappedDescriptor(@NotNull String unmappedDescriptor) {
-        this.unmappedDescriptor = unmappedDescriptor;
+        this.unmappedDescriptor = Objects.requireNonNull(unmappedDescriptor);
     }
 
     @Override
@@ -65,7 +67,7 @@ public static class Mapped implements Component {
         public @NotNull String mappedDescriptor;
 
         public Mapped(@NotNull String mappedDescriptor) {
-            this.mappedDescriptor = mappedDescriptor;
+            this.mappedDescriptor = Objects.requireNonNull(mappedDescriptor);
         }
 
         public void reverseMapped(ClassifiedMappingRemapper remapper) {
@@ -77,7 +79,7 @@ public void reverseMapped(ClassifiedMappingRemapper remapper) {
         }
 
         public void setMappedDescriptor(@NotNull String mappedDescriptor) {
-            this.mappedDescriptor = mappedDescriptor;
+            this.mappedDescriptor = Objects.requireNonNull(mappedDescriptor);
         }
 
         @Override
@@ -102,7 +104,7 @@ public static class Namespaced extends Descriptor {
 
         public Namespaced(@NotNull String unmappedDescriptor, @NotNull String descriptorNamespace) {
             super(unmappedDescriptor);
-            this.descriptorNamespace = descriptorNamespace;
+            this.descriptorNamespace = Objects.requireNonNull(descriptorNamespace);
         }
 
         public @NotNull String getDescriptorNamespace() {
@@ -110,7 +112,7 @@ public Namespaced(@NotNull String unmappedDescriptor, @NotNull String descriptor
         }
 
         public void setDescriptorNamespace(@NotNull String descriptorNamespace) {
-            this.descriptorNamespace = descriptorNamespace;
+            this.descriptorNamespace = Objects.requireNonNull(descriptorNamespace);
         }
 
         @Override
diff --git a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Documented.java b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Documented.java
index 8b3a6d6..c17a49a 100644
--- a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Documented.java
+++ b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Documented.java
@@ -30,4 +30,16 @@ public String getDoc() {
     public void setDoc(String doc) {
         this.doc = Objects.requireNonNull(doc, "null documentation isn't meaningful huh?");
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof Documented that)) return false;
+        return Objects.equals(doc, that.doc);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(doc);
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LineNumber.java b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LineNumber.java
index 75dd5bf..275bf32 100644
--- a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LineNumber.java
+++ b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LineNumber.java
@@ -45,4 +45,16 @@ public int getEndLineNumber() {
     public void setEndLineNumber(int endLineNumber) {
         this.endLineNumber = endLineNumber;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof LineNumber that)) return false;
+        return startLineNumber == that.startLineNumber && endLineNumber == that.endLineNumber;
+    }
+
+    @Override
+    public int hashCode() {
+        return 31 * startLineNumber + endLineNumber;
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LocalVariableTable.java b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LocalVariableTable.java
index 725d8fc..4dc5ce8 100644
--- a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LocalVariableTable.java
+++ b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LocalVariableTable.java
@@ -52,6 +52,18 @@ public void reverseAll(ClassifiedMappingRemapper remapper) {
         values.forEach(v -> v.reverse(remapper));
     }
 
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof LocalVariableTable that)) return false;
+        return Objects.equals(lvt, that.lvt);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(lvt);
+    }
+
     public static class Namespaced implements Component, NameGetter.Namespaced {
         private String unmappedNamespace;
         private String mappedNamespace;
@@ -96,5 +108,17 @@ public void setMappedNamespace(@NotNull String namespace) {
             this.mappedNamespace = Objects.requireNonNull(namespace);
             values.forEach(v -> v.setMappedNamespace(mappedNamespace));
         }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (!(o instanceof Namespaced that)) return false;
+            return Objects.equals(unmappedNamespace, that.unmappedNamespace) && Objects.equals(mappedNamespace, that.mappedNamespace) && Objects.equals(lvt, that.lvt);
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(unmappedNamespace, mappedNamespace, lvt);
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Owned.java b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Owned.java
index 5051378..ba5ef1f 100644
--- a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Owned.java
+++ b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Owned.java
@@ -21,6 +21,8 @@
 import cn.maxpixel.mcdecompiler.mapping.Mapping;
 import cn.maxpixel.mcdecompiler.mapping.collection.ClassMapping;
 
+import java.util.Objects;
+
 public class Owned<T extends Mapping> implements Component {
     public ClassMapping<T> owner;
 
@@ -31,4 +33,16 @@ public ClassMapping<T> getOwner() {
     public void setOwner(ClassMapping<T> owner) {
         this.owner = owner;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof Owned<?> owned)) return false;
+        return Objects.equals(owner.mapping, owned.owner.mapping);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(owner.mapping);
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/StaticIdentifiable.java b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/StaticIdentifiable.java
index 9aa8aaf..4b12806 100644
--- a/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/StaticIdentifiable.java
+++ b/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/StaticIdentifiable.java
@@ -28,4 +28,16 @@ public boolean isStatic() {
     public void setStatic(boolean isStatic) {
         this.isStatic = isStatic;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof StaticIdentifiable that)) return false;
+        return isStatic == that.isStatic;
+    }
+
+    @Override
+    public int hashCode() {
+        return Boolean.hashCode(isStatic);
+    }
 }
\ No newline at end of file