根据jstl中的索引获取arraylist的元素 [英] Getting elements of arraylist based on index in jstl

问题描述

这也许是一件相对简单的事情，但是由于某些原因，我似乎做得不好.

This is perhaps a relatively simple thing to do but for some reason I don't seem to get it right.

如何基于索引从jstl的arrayList中获取元素.

How does one get an element from an arrayList in jstl based on an index.

在纯Java中，可以说我有这个讲坛的人

In pure java, lets say I have this arralist

ArrayList< String > colors = new ArrayList< String >();
   colors.add("red");
   colors.add("orange");
   colors.add("yellow");
   colors.add("green");
   colors.add("blue");

如果我这样做System.out.println(colors.get(1));我从基于arrayList的第一种颜色 在我提供的索引上恰好是red.

if I do System.out.println(colors.get(1)); I get the first color from the arrayList based on the index I supplied which happens to be red.

想知道如何在jstl中实现它.我在jstl中使用了foreach标记，但并没有完全正确.

Wondering how to achieve that in jstl. I played with the foreach tag in jstl but did not quite get it right.

<c:forEach items="colors" var="element">    
 <c:out value="${element.get(1)}"/>
</c:forEach>

推荐答案

当您说colors.get(1);或${element[1]}时，它实际上是指列表中的单个条目.但是，当您使用c:forEach时，它会循环. 这取决于您要实现的目标.如果您只想要第N个元素，请尝试

When you say colors.get(1); or ${element[1]} its actually referrign to single entry in the list. But when you use c:forEach its iterating the loop. It depends on what you are trying to achieve. If you just want the Nth element try

<c:out value="${colors[1]}"/> // This prints the second element of the list

但是您想打印整个元素，就像这样循环

but rather you want to print the entire elements you should go for loop like

<c:forEach items="${colors}" var="element">    
    <c:out value="${element}"/>
</c:forEach>

还请注意，如果您编写类似<c:forEach items="colors" var="element">的文字，则将其字面值视为"colors".因此，如果它是一个变量名，则需要像上例中的${colors}一样在${}中给它命名.

Also please note if you write like <c:forEach items="colors" var="element"> it literally treat the value as "colors". So if its a variable name you need to give it in ${} like ${colors} as depicted in example above.

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