blocks|key|2988996|text|正如文档中明确指出的那样，Character.getNumericValue()以数字的形式返回字符的值。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2988997|如果字符不是数字，则返回-1。|2988998|如果您想要获取已装箱的Character对象的数字Unicode代码点，则需要首先对其进行拆箱：|2988999|int+value+=+(int)c.charValue();|code-block|syntax|javascript|2989000|entityMap^0|D|R|0|C|2|0|B|9|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@$9|U|A|V|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|J|3|K|5|L|7|Z|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|P|$]]

As the documentation clearly states, <code>Character.getNumericValue()</code> returns the character's value as a digit. 
It returns <code>-1</code> if the character is not a digit.

If you want to get the numeric Unicode code point of a boxed <code>Character</code> object, you'll need to unbox it first:

<pre><code>int value = (int)c.charValue();
</code></pre>

blocks|key|2989015|text|来自Character#getNumericValue的Javadoc|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2989016|2989017|如果字符没有数值，则返回-1。如果字符的数值不能表示为非负整数(例如，小数值)，则返回-2。|blockquote|2989018|2989019|2989020|字符%2B没有数值，因此得到的是-1。|2989021|更新：|2989022|基元转换得到43的原因是字符'%2B‘被编码为整数43。|2989023|entityMap^0|2|P|0|0|0|0|0|2|1|0|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|W|8|@]|D|@]|E|$]]|$1|G|3|H|5|I|7|X|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|N|3|O|5|6|7|13|8|@]|D|@]|E|$]]|$1|P|3|Q|5|6|7|14|8|@]|D|@]|E|$]]|$1|R|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|S|$]]

From the Javadoc for <code>Character#getNumericValue</code>:

<blockquote>
 If the character does not have a numeric value, then -1 is returned.
 If the character has a numeric value that cannot be represented as a
 nonnegative integer (for example, a fractional value), then -2 is
 returned.
</blockquote>

The character <code>+</code> does not have a numeric value, so you're getting -1.

Update:

The reason that primitive conversion is giving you 43 is that the the character '+' is encoded as the integer 43.

blocks|key|2776356|text|Character.getNumericValue(c)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2776357|java.lang.Character.getNumericValue(char+ch)返回指定的int字符表示的Unicode值。例如，字符'\u216C'+(罗马数字50+)将返回一个值为50的int。|unstyled|offset|length|style|CODE|2776358|大写('\u0041'+through+'\u005A')、小写('\u0061'+through+'\u007A')和全角变体('\uFF21'+through+'\uFF3A'+and+'\uFF41'+through+'\uFF5A')形式中的字母A-Z的数值介于10到35之间。这与Unicode规范无关，Unicode规范不会将数值分配给这些字符值。|2776359|2776360|此方法返回字符的数字值，作为非负的int值；|blockquote|2776361|2776362|如果字符的数值不是非负整数；|2776363|-1，如果字符没有数值。|2776364|2776365|而here就是这个链接。|2776366|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/7/docs/api/java/lang/Character.html#getNumericValue%2528char%2529^0|0|0|18|1D|3|1Z|8|0|2|R|W|R|1S|1L|0|0|0|0|0|0|0|1|4|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|17|8|@$G|18|H|19|I|J]|$G|1A|H|1B|I|J]|$G|1C|H|1D|I|J]]|9|@]|A|$]]|$1|K|3|L|5|F|7|1E|8|@$G|1F|H|1G|I|J]|$G|1H|H|1I|I|J]|$G|1J|H|1K|I|J]]|9|@]|A|$]]|$1|M|3|-4|5|F|7|1L|8|@]|9|@]|A|$]]|$1|N|3|O|5|P|7|1M|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|F|7|1N|8|@]|9|@]|A|$]]|$1|R|3|S|5|F|7|1O|8|@]|9|@]|A|$]]|$1|T|3|U|5|F|7|1P|8|@]|9|@]|A|$]]|$1|V|3|-4|5|F|7|1Q|8|@]|9|@]|A|$]]|$1|W|3|X|5|F|7|1R|8|@]|9|@$G|1S|H|1T|1|1U]]|A|$]]|$1|Y|3|-4|5|F|7|1V|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]]]

<pre><code>Character.getNumericValue(c)
</code></pre>

The <code>java.lang.Character.getNumericValue(char ch)</code> returns the <code>int</code> value that the specified Unicode character represents. For example, the character <code>'\u216C'</code> (the roman numeral fifty) will return an int with a value of 50.

The letters A-Z in their uppercase <code>('\u0041' through '\u005A')</code>, lowercase <code>('\u0061' through '\u007A')</code>, and full width variant <code>('\uFF21' through '\uFF3A' and '\uFF41' through '\uFF5A')</code> forms have numeric values from 10 through 35. This is independent of the Unicode specification, which does not assign numeric values to these char values.

<blockquote>
 This method returns the numeric value of the character, as a
 nonnegative int value; 
 
 -2 if the character has a numeric value that is not a nonnegative integer; 
 
 -1 if the character has no numeric value.
</blockquote>

And <a href="http://docs.oracle.com/javase/7/docs/api/java/lang/Character.html#getNumericValue%28char%29">here</a> is the link.

blocks|key|172638|text|43是"%2B“符号的十进制ascii数字。这就解释了为什么你能拿回43分。http://en.wikipedia.org/wiki/ASCII|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|172639|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/ASCII^0|10|Y|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]]]]

43 is the dec ascii number for the "+" symbol. That explains why you get a 43 back.
<a href="http://en.wikipedia.org/wiki/ASCII" rel="nofollow">http://en.wikipedia.org/wiki/ASCII</a>

blocks|key|173411|text|请尝试以下任一选项。这些应该是有效的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|173412|int+a+=+Character.getNumericValue('3');
int+a+=+Integer.parseInt(String.valueOf('3');|code-block|syntax|javascript|173413|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try any one of the below. These should work:

<pre><code>int a = Character.getNumericValue('3');
int a = Integer.parseInt(String.valueOf('3');
</code></pre>

blocks|key|173415|text|public+class+IntergerParser+{

public+static+void+main(String[]+args){
String+number+=+"%2B123123";
System.out.println(parseInt(number));
}

private+static+int+parseInt(String+number){
++++char[]+numChar+=+number.toCharArray();
++++int+intValue+=+0;
++++int+decimal+=+1;
++++for(int+index+=+numChar.length+;+index+>+0+;+index+--){
++++++++if(index+==+1+){
++++++++++++if(numChar[index+-+1]+==+'-'){
++++++++++++++++return+intValue+*+-1;
++++++++++++}+else+if(numChar[index+-+1]+==+'%2B'){
++++++++++++++++return+intValue;
++++++++++++}
++++++++}
++++++++intValue+=+intValue+%2B+(((int)numChar[index-1]+-+48)+*+(decimal));
++++++++System.out.println((int)numChar[index-1]+-+48%2B+"+"+%2B+(decimal));
++++++++decimal+=+decimal+*+10;
++++}
++++return+intValue;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|173416|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>public class IntergerParser {

public static void main(String[] args){
String number = "+123123";
System.out.println(parseInt(number));
}

private static int parseInt(String number){
 char[] numChar = number.toCharArray();
 int intValue = 0;
 int decimal = 1;
 for(int index = numChar.length ; index &gt; 0 ; index --){
 if(index == 1 ){
 if(numChar[index - 1] == '-'){
 return intValue * -1;
 } else if(numChar[index - 1] == '+'){
 return intValue;
 }
 }
 intValue = intValue + (((int)numChar[index-1] - 48) * (decimal));
 System.out.println((int)numChar[index-1] - 48+ " " + (decimal));
 decimal = decimal * 10;
 }
 return intValue;
}
</code></pre>

Can someone please explain to me what is going on here:

<pre><code>char c = '+';
int i = (int)c;
System.out.println("i: " + i + " ch: " + Character.getNumericValue(c));
</code></pre>

This prints <code>i: 43 ch:-1</code>. Does that mean I have to rely on primitive conversions to convert <code>char</code> to <code>int</code>? So how can I convert a <code>Character</code> to <code>Integer</code>?

Edit: Yes I know <code>Character.getNumericValue</code> returns <code>-1</code> if it is not a numeric value and that makes sense to me. The question is: why does doing primitive conversions return <code>43</code>?

Edit2: <code>43</code> is the ASCII for <code>+</code>, but I would expect the cast to not succeed just like <code>getNumericValue</code> did not succeed. Otherwise that means there are two semantic equivalent ways to perform the same operation but with different results?

Converting characters to integers in Java

有人能给我解释一下这是怎么回事吗：char c = '+';int i = (int)c;System.out.println("i: " + i + " ch: " + Character.getNumericValue(c));这将打印i: 43 ch:-1。这是否意味着我必须依靠原语转换来将char转换为int？...

问在Java中将字符转换为整数
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