Objects isNull requireNonNullElse requireNonNullElseGet requireNonNull，Java

小咪咪 2023-10-12 18:34 15阅读 0赞

## Objects isNull requireNonNullElse requireNonNullElseGet requireNonNull，Java ##

##  ##

import java.util.Objects;
    import java.util.function.Supplier;
    
    public class Main {
        public static void main(String[] args) {
            String STR = null;
            System.out.println(Objects.isNull(STR));
    
            String s = Objects.requireNonNullElse(STR, "fly");
            System.out.println(s);
    
            String sss = Objects.requireNonNullElseGet(STR, new Supplier<String>() {
                @Override
                public String get() {
                    return "hello,world!";
                }
            });
            System.out.println(sss);
    
            Objects.requireNonNull(STR, "空对象!");
        }
    }

![80001d57e32d442d9aa8ef9498556f09.png][]

Java源代码：

![3f4b5799f5f64d108744496abac813e2.png][]

isNull()实现

![1b5e1ca6eec5499ba9e3063f90df2e79.png][]

[kotlin常用表达式let，?:，as?，?.，!!\_zhangphil的博客-CSDN博客it.todo() //函数内使用it替代object对象访问属性和方法。it.todo() //object不为null，才会执行let函数。当a不为null时,执行大括号里的语句（it肯定不为null）如果a == null ,则为 null。= null，则a.b()如果 a 不是 b，则为 null。如果a 是 b，则 a as b。当a为null时，什么都不执行。如果a==null，抛出空指针。=null时，执行a。当a==null时，执行b。![favicon32.ico][]https://blog.csdn.net/zhangphil/article/details/129264159][kotlin_let_as_._zhangphil_-CSDN_it.todo_ _it_object_it.todo_ _object_null_let_a_null_it_null_a _ null _ null_ null_a.b_ a _ b_ null_a _ b_ a as b_a_null_a_null_null_a_a_null_b_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_129264159]

[kotlin,null let expression\_zhangphil的博客-CSDN博客当a不为null时,执行大括号里的语句（it肯定不为null）如果a == null ,则为 null。= null，则a.b()如果 a 不是 b，则为 null。当a==null时，执行b。当a不为null时,执行大括号里的语句（it肯定不为null）如果a == null ,则为 null。= null，则a.b()如果 a 不是 b，则为 null。当a==null时，执行b。kotlin的let，with，run，apply，also，异同区别\_zhangphil的博客-CSDN博客。![favicon32.ico][]https://blog.csdn.net/zhangphil/article/details/130538081][kotlin_null let expression_zhangphil_-CSDN_a_null_it_null_a _ null _ null_ null_a.b_ a _ b_ null_a_null_b_a_null_it_null_a _ null _ null_ null_a.b_ a _ b_ null_a_null_b_kotlin_let_with_run_apply_also_zhangphil_-CSDN_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_130538081]

[80001d57e32d442d9aa8ef9498556f09.png]: https://img-blog.csdnimg.cn/80001d57e32d442d9aa8ef9498556f09.png
[3f4b5799f5f64d108744496abac813e2.png]: https://img-blog.csdnimg.cn/3f4b5799f5f64d108744496abac813e2.png
[1b5e1ca6eec5499ba9e3063f90df2e79.png]: https://img-blog.csdnimg.cn/1b5e1ca6eec5499ba9e3063f90df2e79.png
[favicon32.ico]: https://g.csdnimg.cn/static/logo/favicon32.ico
[kotlin_let_as_._zhangphil_-CSDN_it.todo_ _it_object_it.todo_ _object_null_let_a_null_it_null_a _ null _ null_ null_a.b_ a _ b_ null_a _ b_ a as b_a_null_a_null_null_a_a_null_b_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_129264159]: https://blog.csdn.net/zhangphil/article/details/129264159
[kotlin_null let expression_zhangphil_-CSDN_a_null_it_null_a _ null _ null_ null_a.b_ a _ b_ null_a_null_b_a_null_it_null_a _ null _ null_ null_a.b_ a _ b_ null_a_null_b_kotlin_let_with_run_apply_also_zhangphil_-CSDN_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_130538081]: https://blog.csdn.net/zhangphil/article/details/130538081