java 消除最后一个逗号和空格
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Eliminating Last Comma & Space
提问by Luke Harding
Here is original prompt:
这是原始提示：
"Write a for loop to print all NUM_VALS elements of array hourlyTemp. Separate elements with a comma and space. Ex: If hourlyTemp = {90, 92, 94, 95}, print: 90, 92, 94, 95
"编写一个 for 循环来打印数组 hourlyTemp 的所有 NUM_VALS 元素。用逗号和空格分隔元素。例如：如果 hourlyTemp = {90, 92, 94, 95}，打印：90, 92, 94, 95
Note that the last element is not followed by a comma, space, or newline."
请注意，最后一个元素后面没有逗号、空格或换行符。”
Here is my code:
这是我的代码：
import java.util.Scanner;
public class PrintWithComma {
public static void main (String [] args) {
final int NUM_VALS = 4;
int[] hourlyTemp = new int[NUM_VALS];
int i = 0;
hourlyTemp[0] = 90;
hourlyTemp[1] = 92;
hourlyTemp[2] = 94;
hourlyTemp[3] = 95;
for (i = 0; i < NUM_VALS; i++) {
System.out.print(hourlyTemp[i] + ", ");
}
System.out.println("");
return;
}
}
My output is "90, 92, 94, 95, " when it should be "90, 92, 94, 95"
我的输出是 "90, 92, 94, 95, " 而它应该是 "90, 92, 94, 95"
How do i eliminate the last comma and space?
我如何消除最后一个逗号和空格？
采纳答案by Atri
Check if the last iteration is reached. If not print the comma, otherwise don't.
检查是否达到了最后一次迭代。如果不打印逗号，否则不要打印。
Replace :
代替 ：
for (i = 0; i < NUM_VALS; i++) {
System.out.print(hourlyTemp[i] + ", ");
}
With:
和：
for (i = 0; i < NUM_VALS; i++) {
if (i == (NUM_VALS - 1)) System.out.print(hourlyTemp[i]);
else System.out.print(hourlyTemp[i] + ", ");
}
回答by fukanchik
Generally you don't know number of values to print up-front (but in your case it's 4). So it is easier to print separator beforeinstead of after. No ifs:
通常，您不知道要预先打印的值的数量（但在您的情况下为 4）。所以更容易打印分隔符before而不是after. 没有if：
String sep="";
for (i = 0; i < NUM_VALS; i++) {
System.out.print(sep + hourlyTemp[i]);
sep=", ";
}
Trick is - first time there is nothing to separate hence separator is empty, later - ", ";
技巧是 - 第一次没有什么可以分开的，因此分隔符是空的，后来 - ", ";
Fits into register, saves branch predictor's work. Calculating if (i == last_value)is not 0 cost as well.
适合寄存器，保存分支预测器的工作。计算if (i == last_value)也不是0成本。
回答by Andrew Tobilko
String delimiter = ", ";
The first way is using java.util.StringJoiner. Additionally, you may specify a prefix and suffix of a result string (for example, (delimiter, "[", "]")).
第一种方法是使用java.util.StringJoiner. 此外，您可以指定结果字符串的前缀和后缀（例如，(delimiter, "[", "]")）。
StringJoiner joiner = new StringJoiner(delimiter);
for (int i : hourlyTemp) joiner.add(Integer.toString(i));
System.out.println(joiner.toString());
The second way is using Stream API.
第二种方式是使用 Stream API。
Arrays.stream(hourlyTemp)
.map(i -> i.toString())
.collect(Collectors.joining(delimiter));
Or the most boring way:
或者最无聊的方式：
for (i = 0; i < NUM_VALS;)
System.out.print(hourlyTemp[i] + (i++ != (NUM_VALS - 1) ? delimiter : ""));
回答by Matthew Wright
As an example, you can put a conditional and just print a blank space once you reach the end.
例如，您可以放置一个条件，并在到达末尾时只打印一个空格。
for(int i=0; i<10; i++) {
System.out.print(i + (i < 10-1 ? ", " : ""));
}
回答by Andy Turner
Split up the value printing and the comma-space printing into two separate statements, and don't print the comma-space for the last value:
将值打印和逗号空间打印拆分为两个单独的语句，并且不要打印最后一个值的逗号空间：
System.out.print(hourlyTemp[i]);
if (i + 1 < NUM_VALS) {
System.out.print(", ");
}
Alternatively, print the first value outside the loop, then print the comma-space first inside the loop:
或者，在循环外打印第一个值，然后在循环内首先打印逗号空间：
System.out.print(hourlyTemp[0]);
for (int i = 1; i < NUM_VALS; ++i) {
System.out.print(", " + hourlyTemp[i]);
}
回答by Ramanlfc
check if ihas reached the last iteration.
检查是否i已到达最后一次迭代。
for (i = 0; i < NUM_VALS; i++) {
if (i == (NUM_VALS - 1))
System.out.print(hourlyTemp[i]);
else
System.out.print(hourlyTemp[i] + ", ");
}
