Polish static final usage for constants

Closes gh-12032

spring-boot-project/spring-boot-cli/src/main/java/org/springframework/boot/cli/command/status/ExitStatus.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,12 +29,12 @@ public final class ExitStatus {
 	/**
 	 * Generic "OK" exit status with zero exit code and {@literal hangup=false}.
 	 */
-	public static ExitStatus OK = new ExitStatus(0, "OK");
+	public static final ExitStatus OK = new ExitStatus(0, "OK");
 
 	/**
 	 * Generic "not OK" exit status with non-zero exit code and {@literal hangup=true}.
 	 */
-	public static ExitStatus ERROR = new ExitStatus(-1, "ERROR", true);
+	public static final ExitStatus ERROR = new ExitStatus(-1, "ERROR", true);
 
 	private final int code;
 

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/env/SpringApplicationJsonEnvironmentPostProcessor.java

@@ -59,12 +59,12 @@ public class SpringApplicationJsonEnvironmentPostProcessor
 	/**
 	 * Name of the {@code spring.application.json} property.
 	 */
-	public static String SPRING_APPLICATION_JSON_PROPERTY = "spring.application.json";
+	public static final String SPRING_APPLICATION_JSON_PROPERTY = "spring.application.json";
 
 	/**
 	 * Name of the {@code SPRING_APPLICATION_JSON} environment variable.
 	 */
-	public static String SPRING_APPLICATION_JSON_ENVIRONMENT_VARIABLE = "SPRING_APPLICATION_JSON";
+	public static final String SPRING_APPLICATION_JSON_ENVIRONMENT_VARIABLE = "SPRING_APPLICATION_JSON";
 
 	private static final String SERVLET_ENVIRONMENT_CLASS = "org.springframework.web."
 			+ "context.support.StandardServletEnvironment";
@@ -176,7 +176,7 @@ public class SpringApplicationJsonEnvironmentPostProcessor
 		private final JsonPropertyValue propertyValue;
 
 		JsonPropertySource(JsonPropertyValue propertyValue, Map<String, Object> source) {
-			super("spring.application.json", source);
+			super(SPRING_APPLICATION_JSON_PROPERTY, source);
 			this.propertyValue = propertyValue;
 		}