Fix #841: addModifiers(Iterable) for TypeSpec.Builder

src/main/java/com/squareup/javapoet/TypeSpec.java

@@ -473,6 +473,19 @@ public Builder addModifiers(Modifier... modifiers) {
       Collections.addAll(this.modifiers, modifiers);
       return this;
     }
+    /**
+     * This is addModifier version for Iterable input.
+
+     * @return Builder
+     */
+    //CS304 Issue link: https://github.com/square/javapoet/issues/841
+    public Builder addModifiers(Iterable<Modifier> modifiers){
+      checkNotNull(modifiers, "modifiers == null");
+      for (Modifier modifier : modifiers){
+        this.modifiers.add(modifier);
+      }
+      return this;
+    }
 
     public Builder addTypeVariables(Iterable<TypeVariableName> typeVariables) {
       checkArgument(typeVariables != null, "typeVariables == null");

src/test/java/com/squareup/javapoet/TypeSpecTest.java

@@ -1999,6 +1999,24 @@ private String toString(TypeSpec typeSpec) {
           .isEqualTo("modifiers contain null");
     }
   }
+//CS304 (manually written) Issue link: https://github.com/square/javapoet/issues/841
+  @Test public void ModifiersListAdditions(){
+    Modifier[] modifiers = {Modifier.PUBLIC, Modifier.FINAL};
+    TypeSpec.Builder builder =
+            TypeSpec.classBuilder("Taco").addModifiers(modifiers);
+
+    assertThat(builder.build().modifiers).containsExactly(Modifier.PUBLIC, Modifier.FINAL);
+  }
+//CS304 (manually written) Issue link: https://github.com/square/javapoet/issues/841
+  @Test public void nullModifiersListAdditions(){
+    try {
+      TypeSpec.classBuilder("Taco")
+              .addModifiers((Iterable<Modifier>) null).build();
+      fail();
+    } catch (NullPointerException e) {
+      assertThat(e.getMessage()).isEqualTo("modifiers == null");
+    }
+  }
 
   @Test public void nullTypeVariablesAddition() {
     try {