Question

当我的程序打印出整数5到1

时，我需要帮助摆脱最后一个逗号

int i;

for (i=10; i>1; --i){
    if ( i%2==0) {
        System.out.print( i/2 + "," );

打印出5,4,3,2,1,

我希望它打印出5,4,3,2,1

Answer 1

一种有效的方法如下：

StringBuilder stringBuilder = new StringBuilder();
for (i=10; i>1; --i){
    if ( i%2==0) {
       stringBuilder.append(i/2);
       stringBuilder.append(",");
    }
}
stringBuilder.setLength(stringBuilder.length()-1);//remove last comma
System.out.println(stringBuilder.toString());

Answer 2

一个简单的if会这样做，但更好，更有效方法是使用StringBuilder

int i = 0;
        for (i = 10; i > 1; --i) {
            if (i % 2 == 0) {
                System.out.print(i / 2);
                if (i > 2) {
                    System.out.print(",");
                }

            }
        }

使用StringBuilder，代码将如下所示

public class Test {

public static void main(String[] args) {
    int i = 0;
    StringBuilder sb = new StringBuilder();
    for (i = 10; i > 1; --i) {
        if (i % 2 == 0) {
            sb.append(i / 2).append(",");
        }
    }
    sb.deleteCharAt(sb.length() - 1);
    System.out.println(sb);
}}

Answer 3

有几种不同的方式，例如写入缓冲区，在打印之前删除最后一个逗号，或者在if == 2 System.out.print（i / 2）时附加if条件;

Answer 4

这是我使用StringBuilder类的通用解决方案：

/**
 * @param x Inclusive from-value
 * @param y Inclusive to-value
 * @param step Gap between numbers
 * @param separator What separates the numbers from each other?
 * @return Numbers from x to y separated by a separator in String format
 */
public static String integersFromXToYWithSeparator(Integer x, Integer y,Integer step, Character separator) {
    StringBuilder builder = new StringBuilder();
    Integer localStep = Math.abs(step);
    if (x < y) {
        while (x <= y) {
            builder.append(x);
            builder.append(separator);
            x+=localStep;
        }
    } else  if (x > y) {
        while (x >= y) {
            builder.append(x);
            builder.append(separator);
            x-=localStep;
        }
    }
    builder.setLength(builder.length()-1);
    return builder.toString();
}

Answer 5

由于java-8有一个StringJoiner类，有助于解决此问题：

StringJoiner joiner = new StringJoiner(",");
for (int i = 10; i > 1; --i) {
    if (i % 2 == 0) {
        joiner.add(String.valueOf(i / 2));
    }
}
System.out.println(joiner.toString());

或使用stream - api

String result =
        IntStream.iterate(10, i -> i - 1)
                .limit(10).filter(i -> i % 2 == 0)
                .map(i -> i / 2)
                .mapToObj(String::valueOf)
                .collect(Collectors.joining(","));

System.out.println(result);

摆脱最后一个逗号

5 个答案: