blocks|key|1389978|text|BigDecimal是不可变的，所以你需要这样做：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1389979|BigDecimal+result+=+test.add(new+BigDecimal(30));
System.out.println(result);|code-block|syntax|javascript|1389980|entityMap^0|0|A|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

The <code>BigDecimal</code> is immutable so you need to do this:

<pre><code>BigDecimal result = test.add(new BigDecimal(30));
System.out.println(result);
</code></pre>

blocks|key|1390014|text|从Java文档的here中可以看出，add返回一个新的BigDecimal：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1390015|BigDecimal+test+=+new+BigDecimal(0);
System.out.println(test);
test+=+test.add(new+BigDecimal(30));
System.out.println(test);
test+=+test.add(new+BigDecimal(45));
System.out.println(test);|code-block|syntax|javascript|1390016|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/j2se/1.5.0/docs/api/java/math/BigDecimal.html^0|8|4|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

It looks like from the Java docs <a href="http://java.sun.com/j2se/1.5.0/docs/api/java/math/BigDecimal.html" rel="noreferrer">here</a> that add returns a new BigDecimal:

<pre><code>BigDecimal test = new BigDecimal(0);
System.out.println(test);
test = test.add(new BigDecimal(30));
System.out.println(test);
test = test.add(new BigDecimal(45));
System.out.println(test);
</code></pre>

blocks|key|1174476|text|BigDecimal+test+=+new+BigDecimal(0);
System.out.println(test);
test+=+test.add(new+BigDecimal(30));
System.out.println(test);
test+=+test.add(new+BigDecimal(45));
System.out.println(test);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1174477|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>BigDecimal test = new BigDecimal(0);
System.out.println(test);
test = test.add(new BigDecimal(30));
System.out.println(test);
test = test.add(new BigDecimal(45));
System.out.println(test);
</code></pre>

blocks|key|1174573|text|这实际上相当简单。只需执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1174574|BigDecimal+test+=+new+BigDecimal(0);
System.out.println(test);
test+=+test.add(new+BigDecimal(30));
System.out.println(test);
test+=+test.add(new+BigDecimal(45));
System.out.println(test);|code-block|syntax|javascript|1174575|另请参阅：BigDecimal#add(java.math.BigDecimal)|offset|length|style|CODE|1174576|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/javase/6/docs/api/java/math/BigDecimal.html#add%2528java.math.BigDecimal%2529^0|0|0|5|10|5|10|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]]|9|@$I|Z|J|10|1|11]]|A|$]]|$1|M|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

It's actually rather easy. Just do this:

<pre><code>BigDecimal test = new BigDecimal(0);
System.out.println(test);
test = test.add(new BigDecimal(30));
System.out.println(test);
test = test.add(new BigDecimal(45));
System.out.println(test);
</code></pre>

See also: <a href="http://java.sun.com/javase/6/docs/api/java/math/BigDecimal.html#add%28java.math.BigDecimal%29" rel="noreferrer"><code>BigDecimal#add(java.math.BigDecimal)</code></a>

blocks|key|1174457|text|BigInteger是不可变的，你需要这样做，|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1174458|++BigInteger+sum+=+test.add(new+BigInteger(30));++
++System.out.println(sum);|code-block|syntax|javascript|1174459|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|$]]

BigInteger is immutable, you need to do this,

<pre><code> BigInteger sum = test.add(new BigInteger(30)); 
 System.out.println(sum);
</code></pre>

blocks|key|1390042|text|//you+can+do+in+this+way...as+BigDecimal+is+immutable+so+cant+set+values+except+in+constructor

BigDecimal+test+=+BigDecimal.ZERO;
BigDecimal+result+=+test.add(new+BigDecimal(30));
System.out.println(result);

result+would+be+30|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1390043|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>//you can do in this way...as BigDecimal is immutable so cant set values except in constructor

BigDecimal test = BigDecimal.ZERO;
BigDecimal result = test.add(new BigDecimal(30));
System.out.println(result);

result would be 30
</code></pre>

blocks|key|1390277|text|BigInteger是不可变的，就像String一样。这意味着一旦对象被创建，我们就不能改变它的内容，但是我们可以重新分配它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1390278|+BigInteger+sum+=+test.add(new+BigInteger(30));++
+System.out.println(sum);|code-block|syntax|javascript|1390279|.add()将返回一个新对象|1390280|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|$]]

BigInteger is immutable, just like Strings.
That means we cannot change it's content once the object is created, but we can re-assign it.
<pre><code> BigInteger sum = test.add(new BigInteger(30)); 
 System.out.println(sum);
</code></pre>
.add() will return a new Object

blocks|key|1174753|text|使用Java8+lambda|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1174754|List<BigDecimal>+items+=+Arrays.asList(a,+b,+c,+.....);

items.stream().filter(Objects::nonNull).reduce(BigDecimal.ZERO,+BigDecimal::add);|code-block|syntax|javascript|1174755|这涵盖了列表中的部分或全部对象为空的情况。|1174756|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|$]]

Using Java8 lambdas 

<pre><code>List&lt;BigDecimal&gt; items = Arrays.asList(a, b, c, .....);

items.stream().filter(Objects::nonNull).reduce(BigDecimal.ZERO, BigDecimal::add);
</code></pre>

This covers cases where the some or all of the objects in the list is null.

blocks|key|1390122|text|BigDecimal+demo+=+new+BigDecimal(15);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1390123|它是不可变的，因为它在内部存储您的输入，即(15)作为final+private+final+BigInteger+intVal;，在字符串创建时使用相同的概念，每个输入最终存储在private+final+char+value[];.So中，没有实现的错误。|unstyled|offset|length|style|CODE|1390124|entityMap^0|0|R|12|2I|R|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|N|8|@$G|O|H|P|I|J]|$G|Q|H|R|I|J]]|9|@]|A|$]]|$1|K|3|-4|5|F|7|S|8|@]|9|@]|A|$]]]|L|$]]

<pre><code>BigDecimal demo = new BigDecimal(15);
</code></pre>

It is immutable beacuse it internally store you input i.e (15) as <code>final private final BigInteger intVal;</code>
and same concept use at the time of string creation every input finally store in 
<code>private final char value[];</code>.So there is no implmented bug.

blocks|key|1390191|text|这只是添加BigDecimals的另一个例子。关键是它们是不可变的，并且只能在构造函数中初始化。代码如下：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1390192|import+java.util.*;
import+java.math.*;

public+class+Main+{
++++public+static+void+main(String[]+args)+{
++++++++Scanner+sc;
++++++++boolean+first_right_number+=+false;
++++++++BigDecimal+initBigDecimal+=+BigDecimal.ZERO;
++++++++BigDecimal+add1+=+BigDecimal.ZERO;
++++++++BigDecimal+add2+=+BigDecimal.ZERO;

++++++++while+(!first_right_number)
++++++++{
++++++++++++System.out.print("Enter+a+first+single+numeric+value:+");
++++++++++++sc+=+new+Scanner(System.in);
++++++++++++if+(sc.hasNextBigDecimal())+
++++++++++++{
++++++++++++++++first_right_number+=+true;
++++++++++++++++add1+=+sc.nextBigDecimal();
++++++++++++}
++++++++}

++++++++boolean+second_right_number+=+false;
++++++++while+(!second_right_number)
++++++++{
++++++++++++System.out.print("Enter+a+second+single+numeric+value:+");
++++++++++++sc+=+new+Scanner(System.in);
++++++++++++if+(sc.hasNextBigDecimal())+
++++++++++++{
++++++++++++++++second_right_number+=+true;
++++++++++++++++add2+=+sc.nextBigDecimal();
++++++++++++}
++++++++}
++++++++BigDecimal+result+=+initBigDecimal.add(add1).add(add2);
++++++++System.out.println("Sum+of+the+2+numbers+is:+"+%2B+result.toString());
++++}
}|code-block|syntax|javascript|1390193|entityMap^0|5|B|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Just another example to add <code>BigDecimals</code>. Key point is that they are immutable and they can be initialized only in the constructor. Here is the code:

<pre><code>import java.util.*;
import java.math.*;

public class Main {
 public static void main(String[] args) {
 Scanner sc;
 boolean first_right_number = false;
 BigDecimal initBigDecimal = BigDecimal.ZERO;
 BigDecimal add1 = BigDecimal.ZERO;
 BigDecimal add2 = BigDecimal.ZERO;

 while (!first_right_number)
 {
 System.out.print("Enter a first single numeric value: ");
 sc = new Scanner(System.in);
 if (sc.hasNextBigDecimal()) 
 {
 first_right_number = true;
 add1 = sc.nextBigDecimal();
 }
 }

 boolean second_right_number = false;
 while (!second_right_number)
 {
 System.out.print("Enter a second single numeric value: ");
 sc = new Scanner(System.in);
 if (sc.hasNextBigDecimal()) 
 {
 second_right_number = true;
 add2 = sc.nextBigDecimal();
 }
 }
 BigDecimal result = initBigDecimal.add(add1).add(add2);
 System.out.println("Sum of the 2 numbers is: " + result.toString());
 }
}
</code></pre>

I want to do some simple sums with some currency values expressed in <code>BigDecimal</code> type. 

<pre><code>BigDecimal test = new BigDecimal(0);
System.out.println(test);
test.add(new BigDecimal(30));
System.out.println(test);
test.add(new BigDecimal(45));
System.out.println(test);
</code></pre>

Obviously I do not understand well the <code>BigDecimal</code> arithmetics, see output behind.

<pre><code>Test
0
0
0
</code></pre>

Can anyone help me out?

Addition for BigDecimal

Java

我想用BigDecimal类型表示的一些货币值做一些简单的求和。BigDecimal test = new BigDecimal(0);System.out.println(test);test.add(new BigDecimal(30));System.out.println(test);test.add(new BigDecimal(45));System.out.println(test)

问BigDecimal的附加功能
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