在if语句中,状态的顺序是否重要?

huangapple go评论78阅读模式
英文:

Does order of the states in the if statement matter?

问题

从代码的第5行开始代码如下

    if (i + 2 < str.length() && str.charAt(i) == 'y' && str.charAt(i + 2) == 'k')

语句的顺序是否重要我在想因为当我赋值 **str = "yak123ya"**

`(i + 2 < str.length() && str.charAt(i) == 'y' && str.charAt(i + 2) == 'k')` 完全正常工作
但是

`(str.charAt(i) == 'y' && str.charAt(i + 2) == 'k' && i + 2 < str.length())` 导致

错误

> StringIndexOutOfBoundsException: String index out of range: 8 (第5行)

以下是你提供的代码部分

    public String stringYak(String str) {
      String result = "";

      for (int i = 0; i < str.length(); i++) {
        if (i + 2 < str.length() && str.charAt(i) == 'y' && str.charAt(i + 2) == 'k') {
          i += 2;
        } else {
          result += str.charAt(i);
        }
      }
      return result;
    }

谢谢
英文:

from line 5 on my code which is,

if (i + 2 &lt; str.length() &amp;&amp; str.charAt(i) == &#39;y&#39; &amp;&amp; str.charAt(i + 2) == &#39;k&#39;)

Does the order of statements matter? I was wondering because

when I assign str = "yak123ya"

(i + 2 &lt; str.length() &amp;&amp; str.charAt(i) == &#39;y&#39; &amp;&amp; str.charAt(i + 2) == &#39;k&#39;) works perfectly fine
but

(str.charAt(i) == &#39;y&#39; &amp;&amp; str.charAt(i + 2) == &#39;k&#39; &amp;&amp; i + 2 &lt; str.length()) causes

error

> StringIndexOutOfBoundsException: String index out of range: 8 (line:5)

public String stringYak(String str) {
  String result = &quot;&quot;;

  for (int i = 0; i &lt; str.length(); i++) {
    if (i + 2 &lt; str.length() &amp;&amp; str.charAt(i) == &#39;y&#39; &amp;&amp; str.charAt(i + 2) == &#39;k&#39;) {
      i += 2;
    } else {
      result += str.charAt(i);
    }
  }
  return result;
}

Thank you!!

答案1

得分: 4

表达式从左到右进行求值,采用短路求值。这意味着当求值表达式 a && b 时,若 a 求值为 false,整个表达式求值为 false,而不会执行 b

在这种情况下,当 i = 6 时,i + 2 < str.length()false,因此不会执行 charAt(6)(也因此不会引发异常)。

英文:

The expressions are evaluated left to right, with short-circuiting. That means when an expression a &amp;&amp; b is evaluated, and a evaluates to false, the whole expression evaluates to false without executing b.

In this case, when i = 6, i + 2 &lt; str.length() is false, and therefore the charAt(6) is not executed (and therefore not throwing an exception).

答案2

得分: 2

是的,当然,顺序很重要。就像在这个 if 语句中:
(i + 2 < str.length() && str.charAt(i) == 'y' && str.charAt(i + 2) == 'k')
如果第一个条件即 i + 2 < str.length() 为假,它将不会检查第二个条件即 str.charAt(i) == 'y',因此不会抛出 StringIndexOutOfBoundsException。

英文:

yes for sure order matters. as in this if statement
(i + 2 < str.length() && str.charAt(i) == 'y' && str.charAt(i + 2) == 'k')
if the first condition which is i + 2 < str.length() is false, it will not check the second condition which is str.charAt(i) == 'y' so it will not throw StringIndexOutOfBoundsException

huangapple
  • 本文由 发表于 2020年10月16日 22:58:59
  • 转载请务必保留本文链接:https://go.coder-hub.com/64391636.html
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定