IDEA中习惯跟踪源码实现逻辑，多次碰到Objects.requireNonNull(T obj)这个方法，改方法主要用于提早判断对象是否为空，以便更早的抛出NPE

平时小组开发中强调程序健壮性，不允许组员的代码中出现明显的NPE,这样多数时候都要写判空逻辑，抛出自定义的异常

我们看下具体的源码：

/**
 * Checks that the specified object reference is not {@code null}.
 * This method is designed primarily for doing parameter validation in methods
 * and constructors, as demonstrated below:
 * <blockquote><pre>
 * public Foo(Bar bar) {
 *     this.bar = Objects.requireNonNull(bar);
 * }
 * </pre></blockquote>
 *
 * @param obj the object reference to check for nullity
 * @param <T> the type of the reference
 * @return {@code obj} if not {@code null}
 * @throws NullPointerException if {@code obj} is {@code null}
 */
public static <T> T requireNonNull(T obj) {
    if (obj == null)
        throw new NullPointerException();
    return obj;
}
解释：检查定义的对象引用不为空。设计该方法主要用来做方法和构造函数中的参数校验
如上，如果直接使用仍然是抛出一个NPE，除了能提早检测和抛出异常，无法直接在业务中使用

继续往下滚动，发现还有这个方法

/**
 * Checks that the specified object reference is not {@code null} and
 * throws a customized {@link NullPointerException} if it is. This method
 * is designed primarily for doing parameter validation in methods and
 * constructors with multiple parameters, as demonstrated below:
 * <blockquote><pre>
 * 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");
 * }
 * </pre></blockquote>
 *
 * @param obj     the object reference to check for nullity
 * @param message detail message to be used in the event that a {@code
 *                NullPointerException} is thrown
 * @param <T> the type of the reference
 * @return {@code obj} if not {@code null}
 * @throws NullPointerException if {@code obj} is {@code null}
 */
public static <T> T requireNonNull(T obj, String message) {
    if (obj == null)
        throw new NullPointerException(message);
    return obj;
}

and throws a customized {@link NullPointerException} if it is：定制的空指针异常

and constructors with multiple parameters ：多参数的构造函数

这样，下次我们想抛出一个自定义的空指针异常的时候,以前是：
if（obj==null）{
　　throw new xxxException("该记录不存在xxxx");
}

现在可以更优雅的写Objects.requireNonNull(T obj,"该记录不存在xxxx")

代码实现区别不大，那么为啥不选择优雅^_^