代码规范

我们大致遵循谷歌的 Java 风格指南 <https://google.github.io/styleguide/javaguide.html>’_ 并有一些微小改动。下面介绍了这些改动。

小技巧

你可以在Eclipse或者IntelliJ IDEA上使用代码规范。详情可以查看Sponge的代码规范<https://github.com/SpongePowered/SpongeAPI/tree/e4abe364d98f6f068018fd96525f88f5fb47a0cf/extra>

• 行结束符

  • 在提交时使用 Unix 风格的行尾 (\n)

    • Windows的git用户可以运行 git config --global core.autocrlf true 来让git进行自动转换

• 列宽

  • Javadoc：80字符

  • 代码：150字符

  • 能提高可读性时可自由换行

• 缩进

  • 使用4个空格来缩进，而不是2个

• 空行

  • 在每个类、接口、枚举等的第一个成员前（例如在 class Example { 之后）和最后一个成员后放置一个空行

• 文件头

  • 文件头必须包含项目的许可头。请使用 gradle 的 licenseFormat 来自动添加。

• 引用

  • 所有引用必须以下列方式分组，每组之间用一个空白行分隔

    • 静态引用

    • 所有其他的引用

    • 对``java``包的引用

    • 对``javax``包的引用

  • 和Google风格中把引用以顶层包分组不同，我们将引用全部分在同一组。

• 异常

  • 对于被忽略的异常，请将异常变量命名为``ignored``

• 字段访问

  • 使用 this 来访问 所有的 字段

• Javadocs

  • 不要使用 @author

  • 用 <p> 和 </p> 包裹段落

  • 每个@语句的描述部分首字母大写。例如 @param name Player to affect ，不要有句号

• 文件结尾

  • 每个文件结尾均应有一空行。

代码约定

• Use 使用 Optional instead of returning null in the API

• 所有能接受 null 的方法参数必须被标注成 @Nullable (位于 javax.*)。所有的方法和参数默认均为 @Nonnull

• 使用 Google Preconditions 来检查 null 和参数。

Gist

尽管我们强烈建议你阅读Google的Java代码约定，但是它们实在是太长了。为了帮助你快速开始，下面是一个格式正确的代码样例：

/*
* This file is part of Sponge, licensed under the MIT License (MIT).
*
* Copyright (c) SpongePowered <https://www.spongepowered.org>
* Copyright (c) contributors
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package org.spongepowered.example;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.inject.Inject;
import org.slf4j.Logger;

import java.util.Optional;
import java.util.Random;
import java.util.concurrent.ThreadLocalRandom;

import javax.annotation.Nullable;

/**
* An example class which generates a new ID based on a specified base string
* and a randomly generated integer.
*
* <p>There is a chance the integer purposely fails to generate, in which case
* you can choose to provide a backup integer.</p>
*/
public class Example {

    private static final long SEED = 4815162342L;

    @Inject
    private Logger logger;

    private final String base;
    private final Random random;

    public Example(String base) {
        checkNotNull(base, "The specified base string cannot be null!");
        this.base = base;
        this.random = ThreadLocalRandom.current();
        this.random.setSeed(SEED);
    }

    /**
    * Generates and returns an ID using the base string specified on creation
    * or the alternative string if specified as well as a randomly generated
    * integer, which purposely fails to generate around 50% of the time.
    *
    * <p>A {@link ThreadLocalRandom} is used to check if the integer should
    * be generated and generates the integer itself if so.</p>
    *
    * @param alternate An alternate base string which will be used if not null
    * @return The generated ID, if available
    */
    public Optional<String> generateId(@Nullable String alternate) {
        if (this.random.nextBoolean()) {
            return Optional.of(alternate == null ? this.base : alternate + " - " + this.random.nextInt());
        }

        return Optional.empty();
    }

    /**
    * Generates and returns an ID using the base string specified on creation,
    * using a randomly generated integer if it was generated successfully, or
    * using the backup integer you specify.
    *
    * <p>A {@link ThreadLocalRandom} is used to check if the integer should
    * be generated and generates the integer itself if so. If it was not
    * generated, that is when your backup integer will be used.</p>
    *
    * @param backup A backup integer to use to create the ID with
    * @return The generated ID using the generated integer or the ID created
    *     using the backup integer specified
    */
    public String generateId(int backup) {
        return generateId(null).orElse(this.base + " - " + backup);
    }

}