for(int i=0;i<list.size();i++){
    System.out.println(list.get(i).getShoutStatus());
}
 
get(i)后面get什么，取决于list中装着什么。
 
如果直接打印list，打印出来的是@balabala，表示list的内存地址。
 

 
 
只有循环打印list中的每一个元素，或者每一个元素中的元素，才能够打印出list中的内容
 

[size=small]方法1) System.out.println(list);

该方法最终会调用java.util.AbstractCollection<E>.toString()方法，遍历list中的元素



方法2) System.out.println(Arrays.toString(list.toArray()));





方法3)使用org.apache.commons.lang.builder.ToStringBuilder.reflectionToString()

Assists in implementing Object.toString() methods.



This class enables a good and consistent toString() to be built for any class or object. This class aims to simplify the process by:



allowing field names 

handling all types consistently 

handling nulls consistently 

outputting arrays and multi-dimensional arrays 

enabling the detail level to be controlled for Objects and Collections 

handling class hierarchies 

To use this class write code as follows:



 public class Person {

 String name;

 int age;

 boolean smoker;



 ...



 public String toString() {

 return new ToStringBuilder(this).

 append("name", name).

 append("age", age).

 append("smoker", smoker).

 toString();

 }

 }



This will produce a toString of the format: Person@7f54[name=Stephen,age=29,smoker=false]



To add the superclass toString, use appendSuper. To append the toString from an object that is delegated to (or any other object), use appendToString.



Alternatively, there is a method that uses reflection to determine the fields to test. Because these fields are usually private, the method, reflectionToString, uses AccessibleObject.setAccessible to change the visibility of the fields. This will fail under a security manager, unless the appropriate permissions are set up correctly. It is also slower than testing explicitly.



A typical invocation for this method would look like:



 public String toString() {

 return ToStringBuilder.reflectionToString(this);

 }



You can also use the builder to debug 3rd party objects:



 System.out.println("An object: " + ToStringBuilder.reflectionToString(anObject));



The exact format of the toString is determined by the ToStringStyle passed into the constructor.



Since:

1.0

Version:

$Id: ToStringBuilder.java 905636 2010-02-02 14:03:32Z niallp $

Author:

Apache Software Foundation

Gary Gregory

Pete Gieser

[/size]

Java快速打印List集合数组的方法
 
一、问题分析
二、解决方法
三、举一反三
 
一、问题分析
 
今天开发完excel导入功能，需要处理数据，插入到表中，使用的数据结构是这样的：
 
	List<String[]> list = new ArrayList<>(10);
 
为了方便调试，我想在控制台（日志）中打印出集合中的元素，由于该元素是数组，与平时的打印方法稍微有点区别，不过差别不大：
 
核心API：
 
	Arrays.toString();
 
二、解决方法
 
使用循环，取出每个list元素，然后利用上述API+强制类型转换：
 
	StringBuffer str = new StringBuffer();
    for (int i = 0; i < list.size(); i++) {
    	str.append(Arrays.toString(((String[])list.get(i))) + "\t");
    }
    logger.info("[POIReadExcel] 读入的数据：" + str.toString());
 
三、举一反三
 
对其它数组或普通集合的元素打印，如果是Object数组，则使用Arrays.toString(obj)，示例：
 
	int[] arr = new int[] {2021, 1, 25};
	System.out.println(Arrays.toString(arr));
		
	String[] str = new String[] {"年年岁岁花相似", "岁岁年年人不同"};
	System.out.println(Arrays.toString(str));
 
如果是集合，则使用集合转数组API——C.toArray()，其中C表示Set、List、Map，示例：
 
		Set<String> set = new HashSet<String>(16);
		set.add("一竿风月");
		set.add("一蓑烟雨");
		set.add("家在钓台西住");
		System.out.println(Arrays.toString(set.toArray()));
		
		List<String> list = new ArrayList<String>(10);
		list.add("纤云弄巧");
		list.add("飞星传恨");
		list.add("银汉迢迢暗度");
		System.out.println(Arrays.toString(list.toArray()));

		
		Map<Integer, String> map = new HashMap<Integer, String>(16);
		map.put(1, "绿蚁新醅酒");
		map.put(2, "红泥小火炉");
		map.put(3, "晚来天欲雪");
		map.put(4, "能饮一杯无");
		System.out.println(Arrays.toString(map.values().toArray()));
 
写在最后
 
本次Java打印集合就介绍到这里啦，我是严光君，咱们下文再见~ 

 
 
相关推荐：
 
Java使用POI导入excel教程
 
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#!/usr/bin/python
# _*_ coding: UTF-8 _*_

t=[1,2,3,[3,4,5,[5,4,3],5],1,2,[4,5],7,4,[6,34]]

def func(L):
        for i in L:
                if(isinstance(i,list)):
                        func(i)
                else:
                        print(i)

func(t)