有人知道为什么我的 else if 语句不起作用吗?

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英文:

Does anyone know why my else if statements are not working?

问题

以下是翻译好的代码部分:

import java.util.*;

public class sortnumber {
  public static void main (String[] args) {
    Scanner scan = new Scanner(System.in);
    int num1, num2, num3, random;
    num1 = scan.nextInt();
    num2 = scan.nextInt();
    num3 = scan.nextInt();
    random = 0;
    if (num1 < num2 && num1 < num3) 
        System.out.print(num1);
        if (num2 < num3)
            System.out.print(num2);
            System.out.print(num3);
        else
            System.out.print(num3);
            System.out.print(num2);            
    else if (num2 < num1 && num2 < num3)
        System.out.print(num2);
        if (num1 < num3)
            System.out.print(num1);
            System.out.print(num3);
        else
            System.out.print(num3);
            System.out.print(num1);
    else if (num3 < num2 && num3 < num1)
        System.out.print(num3);
        if (num2 < num1)
            System.out.print(num2);
            System.out.print(num1);
        else
            System.out.print(num1);
            System.out.print(num2);
  }
}
英文:

This code sorts three numbers from smallest to greatest.
However, my else statements gave me 4 errors, on lines 15, 18, 23, 26, and 31. Does anyone know why this is the case?

import java.util.*;
public class sortnumber {
public static void main (String[] args) {
Scanner scan = new Scanner (System.in);
int num1, num2, num3, random;
num1 = scan.nextInt();
num2 = scan.nextInt();
num3 = scan.nextInt();
random = 0;
if (num1 &lt; num2 &amp;&amp; num1 &lt; num3) 
System.out.print (num1);
if (num2 &lt; num3)
System.out.print (num2);
System.out.print (num3);
else
System.out.print (num3);
System.out.print (num2);            
else if (num2 &lt; num1 &amp;&amp; num2 &lt; num3)
System.out.print (num2);
if (num1 &lt; num3)
System.out.print (num1);
System.out.print (num3);
else
System.out.print (num3);
System.out.print (num1);
else if (num3 &lt; num2 &amp;&amp; num3 &lt; num1)
System.out.print (num3);
if (num2 &lt; num1)
System.out.print (num2);
System.out.print (num1);
else
System.out.print (num1);
System.out.print (num2);
}
}

答案1

得分: 3

由于你没有使用花括号,你的缩进是错误的。实际上你编写的代码是这样的:

random = 0;
if (num1 < num2 && num1 < num3) 
System.out.print(num1);
if (num2 < num3)
System.out.print(num2);
System.out.print(num3);
else                                 // <===== 错误
System.out.print(num3);
System.out.print(num2);
else if (num2 < num1 && num2 < num3) // <===== 错误
System.out.print(num2);
if (num1 < num3)
System.out.print(num1);
System.out.print(num3);
else                                 // <===== 错误
System.out.print(num3);
System.out.print(num1);
else if (num3 < num2 && num3 < num1) // <===== 错误
System.out.print(num3);
if (num2 < num1)
System.out.print(num2);
System.out.print(num1);
else                                 // <===== 错误
System.out.print(num1);
System.out.print(num2);

如果你按照缩进指示添加花括号,代码应该是这样的:

random = 0;
if (num1 < num2 && num1 < num3) {
System.out.print(num1);
if (num2 < num3) {
System.out.print(num2);
System.out.print(num3);
} else {
System.out.print(num3);
System.out.print(num2);
}
} else if (num2 < num1 && num2 < num3) {
System.out.print(num2);
if (num1 < num3) {
System.out.print(num1);
System.out.print(num3);
} else {
System.out.print(num3);
System.out.print(num1);
}
} else if (num3 < num2 && num3 < num1) {
System.out.print(num3);
if (num2 < num1) {
System.out.print(num2);
System.out.print(num1);
} else {
System.out.print(num1);
System.out.print(num2);
}
}

为了避免类似错误,通常建议始终使用花括号。

英文:

Since you don't have curly braces, your indentations are wrong. What you actually coded is this:

random = 0;
if (num1 &lt; num2 &amp;&amp; num1 &lt; num3) 
System.out.print (num1);
if (num2 &lt; num3)
System.out.print (num2);
System.out.print (num3);
else                                 // &lt;===== ERROR
System.out.print (num3);
System.out.print (num2);
else if (num2 &lt; num1 &amp;&amp; num2 &lt; num3) // &lt;===== ERROR
System.out.print (num2);
if (num1 &lt; num3)
System.out.print (num1);
System.out.print (num3);
else                                 // &lt;===== ERROR
System.out.print (num3);
System.out.print (num1);
else if (num3 &lt; num2 &amp;&amp; num3 &lt; num1) // &lt;===== ERROR
System.out.print (num3);
if (num2 &lt; num1)
System.out.print (num2);
System.out.print (num1);
else                                 // &lt;===== ERROR
System.out.print (num1);
System.out.print (num2);

If you add the braces indicated by your indentations, you get this:

random = 0;
if (num1 &lt; num2 &amp;&amp; num1 &lt; num3) {
System.out.print(num1);
if (num2 &lt; num3) {
System.out.print(num2);
System.out.print(num3);
} else {
System.out.print(num3);
System.out.print(num2);
}
} else if (num2 &lt; num1 &amp;&amp; num2 &lt; num3) {
System.out.print(num2);
if (num1 &lt; num3) {
System.out.print(num1);
System.out.print(num3);
} else {
System.out.print(num3);
System.out.print(num1);
}
} else if (num3 &lt; num2 &amp;&amp; num3 &lt; num1) {
System.out.print(num3);
if (num2 &lt; num1) {
System.out.print(num2);
System.out.print(num1);
} else {
System.out.print(num1);
System.out.print(num2);
}
}

In order to prevent mistakes like that, it is commonly recommended to always use curly braces.

答案2

得分: 1

一个if/else if/else语句在其下的代码块超过一行时需要使用花括号({,})。例如,你的第一个if语句是完全有效的。然而,在其余的代码中存在错误。我建议几乎总是使用花括号,即使在if语句下只有一行代码,因为这通常可以使你的代码更易读。

英文:

An if/else if/else statement requires curly braces ({, }) if the block of code under it is more than one line. For example, your first if statement is completely valid. However, errors lie within the rest of the code. I would suggest using curly braces almost always though, as it typically makes your code more readable (even if there is only one line under the if statement).

答案3

得分: 0

你缺少花括号。

Java代码不关心新行从哪里开始以及缩进有多少。取而代之的是使用行尾字符(分号)和花括号。

尽管Java支持无花括号的if/else语句,但它们只将一个语句与ifelse关联起来。最佳实践是始终在条件语句中包含要包含在其中的代码的花括号。

例如,看一下你的第一个嵌套if语句:

if (num1 &lt; num2 &amp;&amp; num1 &lt; num3) {
    System.out.print (num1);
    if (num2 &lt; num3) {
        System.out.print (num2);
        System.out.print (num3);
    }
    else {
        System.out.print (num3);
        System.out.print (num2);            
    }
}

请查看这个页面,了解一些旧但有用的指导:http://www.fredosaurus.com/notes-java/flow/if/30if-braces.html

英文:

You are missing curly braces.

Java code does not pay attention to where new lines start or how much indentation there is. Instead, end-of-line characters (semi-colons) and curly braces are used.

While braceless if/else statements are supported in Java, they only associate one statement with the if or the else. It is considered best practice to always include the curly braces around the code you wish to include in your conditional statement.

For example, taking your first nested if statement:

if (num1 &lt; num2 &amp;&amp; num1 &lt; num3) {
    System.out.print (num1);
    if (num2 &lt; num3) {
        System.out.print (num2);
        System.out.print (num3);
    }
    else {
        System.out.print (num3);
        System.out.print (num2);            
    }
}

Take a look at this page for some old but useful pointers: http://www.fredosaurus.com/notes-java/flow/if/30if-braces.html

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  • 本文由 发表于 2020年10月13日 14:07:35
  • 转载请务必保留本文链接:https://go.coder-hub.com/64329467.html
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