問題描述

打印 char 數組不顯示哈希碼:

Printing a char array does not display a hash code:

class IntChararrayTest{
    public static void main(String[] args){
        int intArray[] = {0,1,2};
        char charArray[] = {'a','b','c'};
        System.out.println(intArray);
        System.out.println(charArray);
    }
}

輸出:

[I@19e0bfd
abc

為什么整數數組打印為哈希碼而不是字符數組?

Why is the integer array printed as a hashcode and not the char array?

推薦答案

首先，char 數組是 Java 中的 Object，就像任何其他類型的數組一樣.只是打印方式不同.

First of all, a char array is an Object in Java just like any other type of array. It is just printed differently.

PrintStream(它是 System.out 實例的類型)有一個特殊版本的 println 用于字符數組 - public void println(char x[]) - 所以它不必為該數組調用 toString.最終調用public void write(char cbuf[], int off, int len)，將數組的字符寫入輸出流.

PrintStream (which is the type of the System.out instance) has a special version of println for character arrays - public void println(char x[]) - so it doesn't have to call toString for that array. It eventually calls public void write(char cbuf[], int off, int len), which writes the characters of the array to the output stream.

這就是為什么為 char[] 調用 println 的行為不同于為其他類型的數組調用它的原因.對于其他數組類型，選擇 public void println(Object x) 重載，它調用 String.valueOf(x)，它調用 x.toString()，它為 int 數組返回類似 [I@19e0bfd 的內容.

That's why calling println for a char[] behaves differently than calling it for other types of arrays. For other array types, the public void println(Object x) overload is chosen, which calls String.valueOf(x), which calls x.toString(), which returns something like [I@19e0bfd for int arrays.

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