Android业务开发中assert的使用_android assert-优快云博客

`1. assert(boolean)`

官方解释是：Throws an AssertionError if the value is false and runtime assertions have been enabled on the JVM using the -ea JVM option.

简单理解是：用来检测执行结果，当boolean为false时，抛出AssertionError，但是需要在开启对应的JVM选项（-ea）时才生效。

2. 使用assert的好处

减少在编码的时候，做的很多ifelse检测判断，以及减少代码层级。比如：某个变量是否为null，某个成员属性是否为true等。

3. assert代码使用

    override fun convert(helper: BaseViewHolder, item: MultiItemEntity?) {
        assert(item is WrapperMultiItemEntity)
        val data = item as WrapperMultiItemEntity
        assert(data.data != null)

        when (helper.itemViewType) {
            MAP.value -> convertExperience(helper, data.data as RecommendInfo)
        }
    }

4. assert思考

之前我们一般是在写单测时才使用到assert，那么在业务代码中使用它是否会产生副作用呢？下面看看反编译后代码：

4.1 Objects.requireNonNull

Checks that the specified object reference is not null and throws a customized NullPointerException if it is. This method is designed primarily for doing parameter validation in methods and constructors with multiple parameters, as demonstrated below:
       public Foo(Bar bar, Baz baz) {
           this.bar = Objects.requireNonNull(bar, "bar must not be null");
           this.baz = Objects.requireNonNull(baz, "baz must not be null");
       }
       
Params:
    obj – the object reference to check for nullity message – detail message to be used in the event that a NullPointerException is thrown
Type parameters:    <T> – the type of the reference
Returns:    obj if not null
Throws:    NullPointerException – if obj is null

    public static <T> T requireNonNull(T obj, String message) {
        if (obj == null)
            throw new NullPointerException(message);
        return obj;
    }