blocks|key|393226|text|正如Java+Language+Specification+§4.12.5+Initial+Values+of+Variables+小节中所述，char属性的默认值确实是'\u0000'+(空字符)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|393227|在我的系统中，行System.out.println('\u0000');打印一个小方块，这意味着它不是一个可打印的字符-正如预期的那样。|393228|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/specs/jls/se7/html/jls-4.html#jls-4.12.5^0|20|4|2D|8|U|10|0|0|8|T|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]|$9|S|A|T|B|C]]|D|@$9|U|A|V|1|W]]|E|$]]|$1|F|3|G|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

The default value of a <code>char</code> attribute is indeed <code>'\u0000'</code> (the null character) as stated in the Java Language Specification, section <a href="http://docs.oracle.com/javase/specs/jls/se7/html/jls-4.html#jls-4.12.5">§4.12.5 Initial Values of Variables </a>.

In my system, the line <code>System.out.println('\u0000');</code> prints a little square, meaning that it's not a printable character - as expected.

blocks|key|609414|text|'\u0000'代表null。所以如果你打印一个未初始化的char变量，你将什么也得不到。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|609415|entityMap^0|0|8|A|4|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

<code>'\u0000'</code> stands for <code>null</code> . So if you print an uninitialized char variable , you'll get nothing.

blocks|key|609344|text|是'\u0000‘。参见here+for+more+information。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|609345|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html^0|C|P|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

It's '\u0000'. See <a href="http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html" rel="nofollow">here for more information</a>.

blocks|key|609476|text|默认字符是int值为0(零)的字符。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|609477|char+NULLCHAR+=+(char)+0；|609478|char+NULLCHAR+=+'\0'；|609479|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

The default char is the character with an int value of 0 (zero).

char NULLCHAR = (char) 0;

char NULLCHAR = '\0';

blocks|key|393458|text|根据下面证明，它很诱人地表示为空格或整数0|type|unstyled|depth|inlineStyleRanges|entityRanges|data|393459|char+c1+=+'\u0000';
System.out.println("*"%2Bc1%2B"*");
System.out.println((int)c1);|code-block|syntax|javascript|393460|但我不会这么说，因为不同的平台或未来可能会有所不同。我真正关心的是我永远不会使用这个默认值，所以在使用任何字符之前，只需检查它是否为\u0000，然后使用它来避免程序中的误解。就这么简单。|393461|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

its tempting say as white space or integer 0 as per below proof

<pre><code>char c1 = '\u0000';
System.out.println("*"+c1+"*");
System.out.println((int)c1);
</code></pre>

but i wouldn't say so because, it might differ it different platforms or in future. What i really care is i ll never use this default value, so before using any char just check it is \u0000 or not, then use it to avoid misconceptions in programs. Its as simple as that.

blocks|key|393528|text|char数据类型的默认值为'\u0000‘(或0)，最大值为'\uffff’(或65,535+)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|393529|您可以看到信息here。|offset|length|393530|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html^0|0|7|4|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

The default value of a char data type is '\u0000' (or 0) and a maximum value of '\uffff' (or 65,535 inclusive).

You can see the info <a href="https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html" rel="nofollow">here</a>.

blocks|key|609768|text|请注意，null和零之间有明显的区别。在http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html+(如上所述)中，语句是:-|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|609769|还有一个特殊的null文本，可以用作任何引用类型的值。null可以赋值给任何变量，但基本类型的变量除外。除了测试空值是否存在之外，您对空值几乎无能为力。因此，null在程序中经常被用作指示某个对象不可用的标记。|609770|这就是为什么下面的语句会给你一个错误，而不是另一个：|609771|char+a=+null；//类型不匹配:无法从null转换为char。|609772|char+b=+0；//有效语法。|609773|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html^0|K|1Z|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|D|3|E|5|6|7|X|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|Y|8|@]|9|@]|C|$]]|$1|H|3|I|5|6|7|Z|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|10|8|@]|9|@]|C|$]]|$1|L|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|M|$N|$5|O|P|Q|C|$R|S]]]]

Note that there is a distinct difference between null and zero. 
In <a href="http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html" rel="nofollow">http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html</a> (referenced above), the statement is made :-

There's also a special null literal that can be used as a value for any reference type. null may be assigned to any variable, except variables of primitive types. There's little you can do with a null value beyond testing for its presence. Therefore, null is often used in programs as a marker to indicate that some object is unavailable.

That is why the following statements will give you an error and not the other :-

char a = null; //Type mismatch: cannot convert from null to char.

char b = 0; //Valid syntax.

blocks|key|609930|text|\u0000是Java中字符类型的缺省值|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|609931|正如其他人提到的，您可以使用比较来检查未初始化变量的值。|609932|char+ch;
if(ch==0)
++++System.out.println("Default+value+is+the+null+character");|code-block|syntax|javascript|609933|entityMap^0|0|6|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

<code>\u0000</code> is the default value for char type in Java

As others mentioned, you can use comparison to check the value of an uninitialized variable.

<pre><code>char ch;
if(ch==0)
 System.out.println("Default value is the null character");
</code></pre>

blocks|key|609831|text|我认为它是'\u00000'，或者只是''，而不是'\u0000'+(第一个有5个0，最后一个有4个0)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|609832|entityMap^0|5|9|J|2|P|8|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

I think it is <code>'\u00000'</code> or just <code>''</code> rather than <code>'\u0000'</code>
(The 1st one has 5 zeros while the last one has four zeroes.)

blocks|key|609987|text|字符的默认值为null，根据Unicode+chart，该值为'\u0000‘。让我们看看打印输出时它是如何工作的。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|609988|public+class+Test_Class+{+++
+++++char+c;
+++++void+printAll()+{++
+++++++System.out.println("c+=+"+%2B+c);
++++}+++
++++public+static+void+main(String[]+args)+{++++
++++Test_Class+f+=+new+Test_Class();++++
++++f.printAll();+++
++++}+}|code-block|syntax|javascript|609989|注意:输出为空。|609990|entityMap|0|LINK|mutability|MUTABLE|url|http://www.unicode.org/charts/PDF/U0000.pdf^0|E|D|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

The default value of char is null which is '\u0000' as per <a href="http://www.unicode.org/charts/PDF/U0000.pdf" rel="nofollow noreferrer">Unicode chart</a>. Let us see how it works while printing out. 

<pre><code>public class Test_Class { 
 char c;
 void printAll() { 
 System.out.println("c = " + c);
 } 
 public static void main(String[] args) { 
 Test_Class f = new Test_Class(); 
 f.printAll(); 
 } }
</code></pre>

Note: The output is blank.

blocks|key|393892|text|正如Java+Language+Specification中所述，char原语类型的默认值是‘\u0000’(空字符)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|393893|“u0000”的快捷方式是“\0”，因此null可以由“u0000”或“\0”表示。|393894|下面的Java程序使用实例字符字段'c‘验证null表示。|393895|public+class+DefaultValueForchar+{++
++++char+c;
++++public+static+void+main(String[]+args)+{
++++++++char+c0+=+'\0';
++++++++char+cu0000+=+'\u0000';
++++++++DefaultValueForchar+obj+=+new+DefaultValueForchar();
++++++++System.out.println(obj.c);
++++++++System.out.println(c0);
++++++++System.out.println(cu0000);
++++++++System.out.println(c0==cu0000);
++++++++System.out.println(obj.c==c0);
++++++++System.out.println(obj.c==cu0000);
++++}

}|code-block|syntax|javascript|393896|📷|atomic|offset|length|393897|​|393898|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/0a7531d2201b2c3c5ee8dfbe857ac704.png|imageAlt^0|0|0|0|0|0|1|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|13|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|M|7|14|8|@]|9|@$N|15|O|16|1|17]]|A|$]]|$1|P|3|Q|5|6|7|18|8|@]|9|@]|A|$]]|$1|R|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|S|$T|$5|U|V|W|A|$X|Y|Z|-4]]]]

The default value of a char primitive type is '\u0000'(null character) as stated in the Java Language Specification.

The shortcut for 'u0000' is '\0', So the null can be represented either by 'u0000' or '\0'.

The below Java program validates null representations using instance char field 'c'.<code>

<pre><code>public class DefaultValueForchar { 
 char c;
 public static void main(String[] args) {
 char c0 = '\0';
 char cu0000 = '\u0000';
 DefaultValueForchar obj = new DefaultValueForchar();
 System.out.println(obj.c);
 System.out.println(c0);
 System.out.println(cu0000);
 System.out.println(c0==cu0000);
 System.out.println(obj.c==c0);
 System.out.println(obj.c==cu0000);
 }

}
</code></pre>

</code>
 <a href="https://i.stack.imgur.com/m4Pd2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/m4Pd2.png" alt="output:"></a>

<pre><code>char c = '\u0000';
</code></pre>

When I print c, it shows 'a' in the command line window. 

So what's the default value of a char type field? 

Someone said '\u0000' means null in unicode; is that right?

what's the default value of char?

Java

char c = '\u0000';当我打印c时，它在命令行窗口中显示'a‘。那么char类型字段的默认值是多少呢？有人说'\u0000‘在unicode中的意思是null，对吗？

问char的默认值是多少？
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回答 11

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问char的默认值是多少？
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