Java将long转换为int。

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英文:

Java converts long to int

问题

以下是要翻译的代码部分:

     import java.util.*;

     public class HelloWorld {

     public static void main(String[] args) {

        Scanner s = new Scanner(System.in);
        
        long N = s.nextLong();
        long[] arr = new long[N];
        
        System.out.println(N);
        
     }
    }

获取到以下错误信息:

HelloWorld.java:12: error: incompatible types: possible lossy conversion from long to int long[] arr = new long[N];

根据我理解,代码中没有涉及到int类型,有人能解释为什么会出现这个错误以及如何解决这个问题吗?

英文:

The following code:

 import java.util.*;

 public class HelloWorld{

 public static void main(String []args){

    Scanner s = new Scanner(System.in);
    
    long N = s.nextLong();
    long[] arr = new long[N];
    
    System.out.println(N);
    
 }
}

Getting this error:

HelloWorld.java:12: error: incompatible types: possible lossy conversion from long to int long[] arr = new long[N];

As far as I understand there is no int involved in the code, can anyone explain why this is happening and how to solve this issue?

答案1

得分: 3

在Java中,数组的大小不能超过int的范围,因此数组创建的大小参数隐式地是一个int。将N改为一个int

来自JLS 15.10.1数组创建表达式(重点在于):

每个维度表达式都会经历一次一元数值提升(§5.6.1)。提升的类型必须是int,否则会导致编译时错误。

英文:

The size of arrays in Java can not exceed the range of an int, so the size parameter for array creation is implicitly an int. Change N to an int.

From JLS 15.10.1 Array Creation Expression (emphasis mine):

> Each dimension expression undergoes unary numeric promotion (§5.6.1). The promoted type must be int, or a compile-time error occurs.

答案2

得分: 2

Array subscripts and sizes in Java must always be int, so in this expression new long[N] the N is converted to int, and because long has a wider range than int, it's a narrowing conversion which must be done explicitly: new long[(int) N]. Or just read N as int: int N = s.nextInt().

英文:

Array subscripts and sizes in Java must always be int, so in this expression new long[N] the N is converted to int, and because long has wider range than int, it's a narrowing conversion which must be done explicitly: new long[(int) N]. Or just read N as int: int N = s.nextInt().

答案3

得分: 1

在这一行中,你正在创建一个大小为N的数组,但在Java中,数组的大小只能是整数,这就是为什么它将N视为一个整数。如果你的意图是创建一个大小为N的数组,你应该将N读取为一个整数。
int N = s.nextInt();
英文:
long[] arr = new long[N];

In this line you are creating an array of size N, but array sizes in Java can only be integers, that's why it's reading N as an int, if your intent is creating an array of N size you should read N as an int

int N = s.nextInt();

答案4

得分: 0

在Java中,数组的最大长度是2,147,483,647(2^31 - 1),这是int的最大长度。因此,数组最大可以容纳int的最大值,无法接受长整型数。

英文:

The maximum length of an array in java is 2,147,483,647 (2^31 - 1) which is the maximum length of int. So implicitly an array can have maximum the value of an int. So it cannot accept a long number.

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  • 本文由 发表于 2020年8月1日 00:06:57
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