問(wèn)題描述

這就是問(wèn)題所在.這段代碼:

String a = "0000";System.out.println(a);char[] b = a.toCharArray();System.out.println(b);

返回

但是這段代碼:

String a = "0000";System.out.println("字符串 a:" + a);char[] b = a.toCharArray();System.out.println("char[] b:" + b);

返回

世界上到底發(fā)生了什么?似乎應(yīng)該有一個(gè)足夠簡(jiǎn)單的解決方案，但我似乎無(wú)法弄清楚.

當(dāng)你說(shuō)

System.out.println(b);

它導(dǎo)致調(diào)用 print(char[] s) 然后 println()

print(char[] s) 的 JavaDoc 說(shuō):

打印一個(gè)字符數(shù)組.字符轉(zhuǎn)換為字節(jié)根據(jù)平臺(tái)的默認(rèn)字符編碼，而這些字節(jié)完全按照 write(int) 方法的方式寫入.

所以它會(huì)逐字節(jié)打印出來(lái).

當(dāng)你說(shuō)

System.out.println("char[] b: " + b);

這會(huì)導(dǎo)致調(diào)用 print(String)，因此您實(shí)際上正在做的是將 String 附加到 Object它在 Object 上調(diào)用 toString() - 這與默認(rèn)情況下的所有 Object 以及在 Array 的情況下一樣，打印引用的值(內(nèi)存地址).

你可以這樣做:

System.out.println("char[] b: " + new String(b));

請(qǐng)注意，這是錯(cuò)誤的"，因?yàn)槟魂P(guān)心編碼并且使用系統(tǒng)默認(rèn)值.盡早了解編碼.

Here's the problem. This code:

String a = "0000";
 System.out.println(a);
char[] b = a.toCharArray();
 System.out.println(b);

returns

0000
0000

But this code:

String a = "0000";
 System.out.println("String a: " + a);
char[] b = a.toCharArray();
 System.out.println("char[] b: " + b);

returns

String a: 0000
char[] b: [C@56e5b723

What in the world is going on? Seems there should be a simple enough solution, but I can't seem to figure it out.

When you say

System.out.println(b);

It results in a call to print(char[] s) then println()

The JavaDoc for print(char[] s) says:

Print an array of characters. The characters are converted into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.

So it performs a byte-by-byte print out.

When you say

System.out.println("char[] b: " + b);

It results in a call to print(String), and so what you're actually doing is appending to a String an Object which invokes toString() on the Object -- this, as with all Object by default, and in the case of an Array, prints the value of the reference (the memory address).

You could do:

System.out.println("char[] b: " + new String(b));

Note that this is "wrong" in the sense that you're not paying any mind to encoding and are using the system default. Learn about encoding sooner rather than later.

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