java 从 ArrayList 创建格式化字符串
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Create formatted string from ArrayList
提问by StefanE
Consider following code:
考虑以下代码：
ArrayList<Integer> aList = new ArrayList<Integer>();
aList.add(2134);
aList.add(3423);
aList.add(4234);
aList.add(343);
String tmpString = "(";
for(int aValue : aList) {
tmpString += aValue + ",";
}
tmpString = (String) tmpString.subSequence(0, tmpString.length()-1) + ")";
System.out.println(tmpString);
My result here is (2134,3423,4234,343) as expected..
我的结果是 (2134,3423,4234,343) 正如预期的那样..
I do replace the last comma with the ending ) to get expected result. Is there a better way of doing this in general?
我确实用结尾替换了最后一个逗号 ) 以获得预期的结果。一般来说，有没有更好的方法来做到这一点？
回答by Rob Hruska
You could use Commons Lang:
您可以使用Commons Lang：
String tmpString = "(" + StringUtils.join(aList, ",") + ")";
Alternatively, if you can't use external libraries:
或者，如果您不能使用外部库：
StringBuilder builder = new StringBuilder("(");
for (int aValue : aList) builder.append(aValue).append(",");
if (aList.size() > 0) builder.deleteCharAt(builder.length() - 1);
builder.append(")");
String tmpString = builder.toString();
回答by MrMeszaros
Since Java 8you can also do:
从Java 8 开始，您还可以执行以下操作：
ArrayList<Integer> intList = new ArrayList<Integer>();
intList.add(2134);
intList.add(3423);
intList.add(4234);
intList.add(343);
String prefix = "(";
String infix = ", ";
String postfix = ")";
StringJoiner joiner = new StringJoiner(infix, prefix, postfix);
for (Integer i : intList)
joiner.add(i.toString());
System.out.println(joiner.toString());
回答by jzd
You will have to replace the last comma with a ')'. But use a StringBuilder instead of adding strings together.
您必须用“)”替换最后一个逗号。但是使用 StringBuilder 而不是将字符串添加在一起。
回答by Aravind Yarram
How about this from google-guava
这个来自google-guava怎么样
String joinedStr = Joiner.on(",").join(aList);
System.out.println("("+JjoinedStr+")");
回答by DanM
Building off Mateusz's Java 8 example, there's an example in the StringJoinerJavaDoc that nearly does what OP wants. Slightly tweaked it would look like this:
构建Mateusz的 Java 8 示例，StringJoinerJavaDoc 中有一个示例几乎可以满足OP 的要求。稍微调整一下，它看起来像这样：
List<Integer> numbers = Arrays.asList(1, 2, 3, 4);
String commaSeparatedNumbers = numbers.stream()
.map(i -> i.toString())
.collect( Collectors.joining(",","(",")") );
回答by Qwerky
If you used an Iteratoryou could test hasNext()inside your loop to determine whether you needed to append a comma.
如果您使用了Iterator，则可以hasNext()在循环内进行测试以确定是否需要附加逗号。
StringBuilder builder = new StringBuilder();
builder.append("(");
for(Iterator<Integer> i=aList.iterator(); i.hasNext();)
{
builder.append(i.next().toString());
if (i.hasNext()) builder.append(",");
}
builder.append(")");
回答by m.edmondson
for(int aValue : aList) {
if (aValue != aList.Count - 1)
{
tmpString += aValue + ",";
}
else
{
tmpString += aValue + ")";
}
}
Perhaps?
也许？
