JAVA中判断数据不为空后执行数据操作、防止空指针报错的工具类，safes工具类

àì夳堔傛蜴生んèń 2023-01-16 09:49 129阅读 0赞

问题描述：

//问题描述， 由于集合为null
            //会报Exception in thread "main" java.lang.NullPointerException
            List<User> userList = null;
            userList.forEach(user->{
                user.setUserName("李四");
            });
            System.out.println(userList);
    
            //使用该工具类解决问题
            List<User> userList2 = null;
            Safes.of(userList2).forEach(user->{
                user.setUserName("李四");
            });
            System.out.println(userList2);

工具类代码：

package com.zcst.common.utils;
    
    import com.baomidou.mybatisplus.core.toolkit.CollectionUtils;
    import com.google.common.collect.Lists;
    import com.google.common.collect.Maps;
    import com.google.common.collect.Sets;
    
    import java.math.BigDecimal;
    import java.util.*;
    import java.util.function.Consumer;
    
    /**
     * @author Administrator
     */
    public class Safes {
    
        public static <K, V> Map<K, V> of(Map<K, V> source) {
            return (Map) Optional.ofNullable(source).orElse(Maps.newHashMapWithExpectedSize(0));
        }
    
        public static <T> Iterator<T> of(Iterator<T> source) {
            return (Iterator) Optional.ofNullable(source).orElse((Iterator<T>) Lists.newArrayListWithCapacity(0).iterator());
        }
    
        public static <T> Collection<T> of(Collection<T> source) {
            return (Collection) Optional.ofNullable(source).orElse(Lists.newArrayListWithCapacity(0));
        }
    
        public static <T> Iterable<T> of(Iterable<T> source) {
            return (Iterable) Optional.ofNullable(source).orElse(Lists.newArrayListWithCapacity(0));
        }
    
        public static <T> List<T> of(List<T> source) {
            return (List) Optional.ofNullable(source).orElse(Lists.newArrayListWithCapacity(0));
        }
    
        public static <T> Set<T> of(Set<T> source) {
            return (Set) Optional.ofNullable(source).orElse(Sets.newHashSetWithExpectedSize(0));
        }
    
        public static BigDecimal of(BigDecimal source) {
            return (BigDecimal) Optional.ofNullable(source).orElse(BigDecimal.ZERO);
        }
    
        public static String of(String source) {
            return (String) Optional.ofNullable(source).orElse("");
        }
    
        public static String of(String source, String defaultStr) {
            return (String) Optional.ofNullable(source).orElse(defaultStr);
        }
    
        public static <T> T first(Collection<T> source) {
            if (CollectionUtils.isEmpty(source)) {
                return null;
            }
            T t = null;
            Iterator<T> iterator = source.iterator();
            if (iterator.hasNext()) {
                t = iterator.next();
            }
            return t;
        }
    
        public static void run(Runnable runnable, Consumer<Throwable> error) {
            try {
                runnable.run();
            } catch (Throwable t) {
                error.accept(t);
            }
        }
    
        static String trimToEmpty(String str) {
            return str == null ? "" : str.trim();
        }
    }