怎么从ArrayList中取出boolean类型的值？ singlion 2014-05-13 09:04:36 我有一段代码是这样的 if(params.get(i) instanceof Boolean){ p.setBoolean(i+1, Boolean.parseBoolean((String)params.get(i))); } 这段代码没有错吧？但是就是执行时就是出错。 我这样写的原因，因为params是ArrayList<Object>，所以取出的是Object类型，但是Boolean类的方法中没有把Object转换成Boolean的方法，所以只能先转成String再转Boolean。 但是执行的时候报错 java.lang.Boolean cannot be cast to java.lang.String 这不是进入怪圈了吗，想不通啊…… ...全文 305 6 打赏 收藏 怎么从ArrayList<Object>中取出boolean类型的值？ 我有一段代码是这样的 if(params.get(i) instanceof Boolean){ p.setBoolean(i+1, Boolean.parseBoolean((String)params.get(i))); } 这段代码没有错吧？但是就是执行时就是出错。 我这样写的原因，因为params是ArrayList，所以取出的是Object类型，但是Boolean类的方法中没有把Object转换成Boolean的方法，所以只能先转成String再转Boolean。 但是 复制链接 扫一扫 分享 转发到动态 举报 写回复 配置赞助广告取 消 确 定 用AI写文章 6 条回复 切换为时间正序 请发表友善的回复… 发表回复 打赏红包 需支付: 0.00 元 取 消 确 定 singlion 2014-05-13 打赏举报 回复 晕，原来这么简单…… singlion 2014-05-13 打赏举报 回复 引用 1 楼 lymoge 的回复:为什么要转成String而不直接转成Boolean呢。 怎么直接转成Boolean？ Boolean类中没有转换Object为boolean的方法啊 Magical茏 2014-05-13 打赏举报 回复 楼主试试看 if(params.get(i) instanceof Boolean){ p.setBoolean(i+1, (Boolean)params.get(i)); } if(params.get(i) instanceof Boolean){ p.setBoolean(i+1, Boolean.parseBoolean(params.get(i).toString())); } WayneXuan 2014-05-13 打赏举报 回复 Boolean对象强转String当然会异常 if(params.get(i) instanceof Boolean){ p.setBoolean(i+1, (Boolean)params.get(i)); } ilmlife 2014-05-13 打赏举报 回复 调用object的toString方法 lymoge 2014-05-13 打赏举报 回复 为什么要转成String而不直接转成Boolean呢。 Java List＜Object＞、List＜Map＜String,Object＞＞Stream流的相关用法 通过集合的stream()方法的collect方法，填入对应参数进行获取。通过集合的stream()方法取出对象中的某一列。通过集合的stream()方法取出对象中的某一列。通过Stream.of()方法创建动态集合。为方便测试此处加了一条数据。 Arraylist 集合 List接口： 有序的、不唯一 ArrayList： 特点： 有序、不唯一 数据结构： Object数组 ArrayList：包装类 作用一：ArrayList是基于Object[]实现的，所以该只能装引用数据类型，基本数据类型要想装进集合，需要将基本数据类型进行类的包装。 作用二：包装类中有将String类型转换为对应的基本数据类型的方法。 ArrayList的基本用法和特点 特点： ... java - 实现list「object」中某个属性的对比 1. List list = new ArrayList(); 报错：Type mismatch: cannot convert from ArrayList<?> to List<String> 原因：导入的包导错了，导成了： java.awt.List; 解决办法： import java.util.List; 2.List的一些简单操作 https://www.cnblogs.com/czq520/p/11647548.html 3.List中Object的 两个list 比较 得到相同数据 差异数据 package com.lizi.admin.utils.contrast;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method; public class EntityUtil { private static String GET_METHOD_PREFIX = "get"; ... java中ArrayList集合 数组可以保存多个元素，但在某些情况下无法确定到底要保存多少个元素，此时数组将不再适用，因为数组的长度不可变。例如，要保存一个学校的学生，由于不停有新生来报道，同时也有学生毕业离开学校，这时学生的数目很难确定。为了保存这些数目不确定的元素，JDK中提供了一系列特殊的类，这些类可以存储任意类型的元素，并且长度可变，统称为集合。ArrayList集合是程序中最常见的一种集合，它属于引用数据类型（类）。在... 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[singlion]

我有一段代码是这样的

if(params.get(i) instanceof Boolean){
	p.setBoolean(i+1, Boolean.parseBoolean((String)params.get(i)));
}

这段代码没有错吧？但是就是执行时就是出错。
我这样写的原因，因为params是ArrayList<Object>，所以取出的是Object类型，但是Boolean类的方法中没有把Object转换成Boolean的方法，所以只能先转成String再转Boolean。

但是执行的时候报错 java.lang.Boolean cannot be cast to java.lang.String

这不是进入怪圈了吗，想不通啊……

[lymoge]

为什么要转成String而不直接转成Boolean呢。

[ilmlife]

调用object的toString方法

[WayneXuan]

Boolean对象强转String当然会异常

if(params.get(i) instanceof Boolean){
	p.setBoolean(i+1, (Boolean)params.get(i));
}

[Magical茏]

楼主试试看

if(params.get(i) instanceof Boolean){
		    p.setBoolean(i+1, (Boolean)params.get(i));
		}

if(params.get(i) instanceof Boolean){
		    p.setBoolean(i+1, Boolean.parseBoolean(params.get(i).toString()));
		}

[singlion]

引用 1 楼 lymoge 的回复:

为什么要转成String而不直接转成Boolean呢。

怎么直接转成Boolean？ Boolean类中没有转换Object为boolean的方法啊

[singlion]

晕，原来这么简单……