Use @FormatString and @FormatMethod annotations.

This introduces a compile-time-only dependency on errorprone
annotations.

Also fixes a bug identified by errorprone when these annotations were
added.

build.gradle

@@ -29,6 +29,8 @@ dependencies {
     testCompile 'junit:junit:4.12'
     testCompile 'com.google.truth:truth:0.24'
 
+    compile 'com.google.errorprone:error_prone_annotations:2.4.0'
+
     // Cobertura requires slf4j at runtime
     testRuntime 'org.slf4j:slf4j-api:1.7.10'
 

src/main/java/au/com/southsky/jfreesane/Preconditions.java

@@ -1,9 +1,13 @@
 package au.com.southsky.jfreesane;
 
+import com.google.errorprone.annotations.FormatMethod;
+import com.google.errorprone.annotations.FormatString;
+
 final class Preconditions {
   private Preconditions() {}
 
-  static void checkState(boolean state, String message, Object... args) {
+  @FormatMethod
+  static void checkState(boolean state, @FormatString String message, Object... args) {
     if (!state) {
       throw new IllegalStateException(String.format(message, args));
     }
@@ -27,7 +31,8 @@ static void checkArgument(boolean arg) {
     }
   }
 
-  static void checkArgument(boolean arg, String message, Object... args) {
+  @FormatMethod
+  static void checkArgument(boolean arg, @FormatString String message, Object... args) {
     if (!arg) {
       throw new IllegalArgumentException(String.format(message, args));
     }

src/main/java/au/com/southsky/jfreesane/SaneOption.java

@@ -491,7 +491,7 @@ public void setButtonValue() throws IOException, SaneException {
    */
   public double setFixedValue(double value) throws IOException, SaneException {
     Preconditions.checkArgument(
-        value >= -32768 && value <= 32767.9999, "value %d is out of range", value);
+        value >= -32768 && value <= 32767.9999, "value %f is out of range", value);
     SaneWord wordValue = SaneWord.forFixedPrecision(value);
     ControlOptionResult result = writeOption(wordValue);
     Preconditions.checkState(