blocks|key|1647078|text|如果要返回两个对象，通常需要返回封装这两个对象的单个对象。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1647079|您可以返回NamedObject对象列表，如下所示：|offset|length|style|CODE|1647080|public+class+NamedObject<T>+{
++public+final+String+name;
++public+final+T+object;

++public+NamedObject(String+name,+T+object)+{
++++this.name+=+name;
++++this.object+=+object;
++}
}|code-block|syntax|javascript|1647081|然后，您可以很容易地返回一个List<NamedObject<WhateverTypeYouWant>>。|1647082|还有:为什么要返回逗号分隔的名称列表，而不是List<String>？或者更好的方法是返回一个Map<String,TheObjectType>，其中的键是对象的名称和值(除非您的对象有指定的顺序，在这种情况下，NavigableMap可能就是您想要的。|1647083|entityMap^0|0|5|B|0|0|E|12|0|M|C|1B|P|2Y|C|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@$D|U|E|V|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|W|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|X|8|@$D|Y|E|Z|F|G]]|9|@]|A|$]]|$1|O|3|P|5|6|7|10|8|@$D|11|E|12|F|G]|$D|13|E|14|F|G]|$D|15|E|16|F|G]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|R|$]]

If you want to return two objects you usually want to return a single object that encapsulates the two objects instead.

You could return a List of <code>NamedObject</code> objects like this:

<pre><code>public class NamedObject&lt;T&gt; {
 public final String name;
 public final T object;

 public NamedObject(String name, T object) {
 this.name = name;
 this.object = object;
 }
}
</code></pre>

Then you can easily return a <code>List&lt;NamedObject&lt;WhateverTypeYouWant&gt;&gt;</code>.

Also: Why would you want to return a comma-separated list of names instead of a <code>List&lt;String&gt;</code>? Or better yet, return a <code>Map&lt;String,TheObjectType&gt;</code> with the keys being the names and the values the objects (unless your objects have specified order, in which case a <code>NavigableMap</code> might be what you want.

blocks|key|1432184|text|所有可能的解决方案都将是杂乱无章的(比如容器对象，你的HashMap想法，通过数组实现的“多个返回值”)。我建议从返回的列表中重新生成逗号分隔的列表。代码最终将变得更加整洁。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1432185|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

All possible solutions will be a kludge (like container objects, your HashMap idea, “multiple return values” as realized via arrays). I recommend regenerating the comma-separated list from the returned List. The code will end up being a lot cleaner.

blocks|key|1432254|text|在Java+5之前，我有点同意Map解决方案并不理想。它不会给你提供编译时类型检查，所以可能会在运行时导致问题。然而，在Java5中，我们有泛型类型。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1432255|因此，您的方法可能如下所示：|1432256|public+Map<String,+MyType>+doStuff();|code-block|syntax|javascript|1432257|当然，MyType是您要返回的对象类型。|1432258|基本上，我认为在这种情况下，返回一个Map是正确的解决方案，因为这正是您想要返回的-字符串到对象的映射。|1432259|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Before Java 5, I would kind of agree that the Map solution isn't ideal. It wouldn't give you compile time type checking so can cause issues at runtime. However, with Java 5, we have Generic Types.

So your method could look like this:

<pre><code>public Map&lt;String, MyType&gt; doStuff();
</code></pre>

MyType of course being the type of object you are returning.

Basically I think that returning a Map is the right solution in this case because that's exactly what you want to return - a mapping of a string to an object.

blocks|key|1647257|text|在我看来，这里实际上有三个选择，解决方案取决于上下文。您可以选择在生成列表的方法中实现名称的构造。这是你的选择，但我不认为这是最好的选择。您在生产者方法中创建了与不需要存在的消费方法的耦合。其他调用者可能不需要额外的信息，您将为这些调用者计算额外的信息。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1647258|或者，您可以让调用方法计算名称。如果只有一个调用者需要此信息，您可以到此为止。您没有额外的依赖项，虽然涉及到一些额外的计算，但您避免了使您的构造方法过于具体。这是一个很好的权衡。|1647259|最后，您可以让列表本身负责创建名称。如果计算需要由多个调用者完成，这是我会走的路线。我认为这将创建名称的责任与与对象本身最密切相关的类放在一起。|1647260|在后一种情况下，我的解决方案是创建一个专门的List类，它返回它所包含的对象名称的逗号分隔字符串。使类足够智能，以便在向类添加对象和从中删除对象时动态构造名称字符串。然后返回该列表的一个实例，并根据需要调用名称生成方法。尽管简单地将名称的计算延迟到第一次调用该方法并存储它(惰性加载)几乎同样有效(也更简单)。如果添加/删除对象，只需删除计算值，并在下一次调用时重新计算它。|1647261|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|L|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|M|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

As I see it there are really three choices here and the solution depends on the context. You can choose to implement the construction of the name in the method that produces the list. This is the choice you've chosen, but I don't think it is the best one. You are creating a coupling in the producer method to the consuming method that doesn't need to exist. Other callers may not need the extra information and you would be calculating extra information for these callers.

Alternatively, you could have the calling method calculate the name. If there is only one caller that needs this information, you can stop there. You have no extra dependencies and while there is a little extra calculation involved, you've avoided making your construction method too specific. This is a good trade-off.

Lastly, you could have the list itself be responsible for creating the name. This is the route I would go if the calculation needs to be done by more than one caller. I think this puts the responsibility for the creation of the names with the class that is most closely related to the objects themselves.

In the latter case, my solution would be to create a specialized List class that returns a comma-separated string of the names of objects that it contains. Make the class smart enough that it constructs the name string on the fly as objects are added and removed from it. Then return an instance of this list and call the name generation method as needed. Although it may be almost as efficient (and simpler) to simply delay calculation of the names until the first time the method is called and store it then (lazy loading). If you add/remove an object, you need only remove the calculated value and have it get recalculated on the next call.

blocks|key|1432382|text|在C%2B%2B+(STL)中，有一个用于绑定两个对象的pair类。在Java+Generics中，一对类是不可用的，尽管它有一些demand。不过，您可以很容易地自己实现它。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1432383|然而，我同意其他一些答案，即如果您需要从一个方法返回两个或更多对象，最好将它们封装在一个类中。|1432384|entityMap|0|LINK|mutability|MUTABLE|url|http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6229146^0|1P|6|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

In C++ (STL) there is a pair class for bundling two objects. In Java Generics a pair class isn't available, although there is some <a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6229146" rel="nofollow noreferrer">demand</a> for it. You could easily implement it yourself though.

I agree however with some other answers that if you need to return two or more objects from a method, it would be better to encapsulate them in a class.

blocks|key|1647369|text|当我用Java编写代码时，我几乎总是最终定义n-Tuple类。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1647370|public+class+Tuple2<T1,T2>+{
++private+T1+f1;
++private+T2+f2;
++public+Tuple2(T1+f1,+T2+f2)+{
++++this.f1+=+f1;+this.f2+=+f2;
++}
++public+T1+getF1()+{return+f1;}
++public+T2+getF2()+{return+f2;}
}|code-block|syntax|javascript|1647371|我知道这有点难看，但它是有效的，而且你只需要定义一次你的元组类型。元组是Java真正缺乏的东西。|1647372|编辑:+David+Hanak的示例更加优雅，因为它避免了定义getter，并且仍然保持对象的不可变性。|1647373|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I almost always end up defining n-Tuple classes when I code in Java. For instance:

<pre><code>public class Tuple2&lt;T1,T2&gt; {
 private T1 f1;
 private T2 f2;
 public Tuple2(T1 f1, T2 f2) {
 this.f1 = f1; this.f2 = f2;
 }
 public T1 getF1() {return f1;}
 public T2 getF2() {return f2;}
}
</code></pre>

I know it's a bit ugly, but it works, and you just have to define your tuple types once. Tuples are something Java really lacks.

EDIT: David Hanak's example is more elegant, as it avoids defining getters and still keeps the object immutable.

blocks|key|1432503|text|或者，在我想要从一个方法返回许多东西的情况下，我有时会使用回调机制而不是容器。这在我不能提前指定将生成多少对象的情况下工作得很好。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1432504|对于您的特定问题，它将如下所示：|1432505|public+class+ResultsConsumer+implements+ResultsGenerator.ResultsCallback
{
++++public+void+handleResult(+String+name,+Object+value+)
++++{
++++++++...+
++++}
}

public+class+ResultsGenerator
{
++++public+interface+ResultsCallback
++++{
++++++++void+handleResult(+String+aName,+Object+aValue+);
++++}

++++public+void+generateResults(+ResultsGenerator.ResultsCallback+aCallback+)
++++{
++++++++Object+value+=+null;
++++++++String+name+=+null;

++++++++...

++++++++aCallback.handleResult(+name,+value+);
++++}
}|code-block|syntax|javascript|1432506|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Alternatively, in situations where I want to return a number of things from a method I will sometimes use a callback mechanism instead of a container. This works very well in situations where I cannot specify ahead of time just how many objects will be generated. 

With your particular problem, it would look something like this:

<pre><code>public class ResultsConsumer implements ResultsGenerator.ResultsCallback
{
 public void handleResult( String name, Object value )
 {
 ... 
 }
}

public class ResultsGenerator
{
 public interface ResultsCallback
 {
 void handleResult( String aName, Object aValue );
 }

 public void generateResults( ResultsGenerator.ResultsCallback aCallback )
 {
 Object value = null;
 String name = null;

 ...

 aCallback.handleResult( name, value );
 }
}
</code></pre>

blocks|key|1432564|text|将散列传递到方法中并填充它......|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1432565|public+void+buildResponse(字符串数据，映射响应)；|1432566|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

PASS A HASH INTO THE METHOD AND POPULATE IT......

public void buildResponse(String data, Map response);

blocks|key|1432579|text|public+class+MultipleReturnValues+{

++++public+MultipleReturnValues()+{
++++}

++++public+static+void+functionWithSeveralReturnValues(final+String[]+returnValues)+{
++++++++returnValues[0]+=+"return+value+1";
++++++++returnValues[1]+=+"return+value+2";
++++}

++++public+static+void+main(String[]+args)+{
++++++++String[]+returnValues+=+new+String[2];
++++++++functionWithSeveralReturnValues(returnValues);
++++++++System.out.println("returnValues[0]+=+"+%2B+returnValues[0]);
++++++++System.out.println("returnValues[1]+=+"+%2B+returnValues[1]);
++++}

}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1432580|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 MultipleReturnValues {

 public MultipleReturnValues() {
 }

 public static void functionWithSeveralReturnValues(final String[] returnValues) {
 returnValues[0] = "return value 1";
 returnValues[1] = "return value 2";
 }

 public static void main(String[] args) {
 String[] returnValues = new String[2];
 functionWithSeveralReturnValues(returnValues);
 System.out.println("returnValues[0] = " + returnValues[0]);
 System.out.println("returnValues[1] = " + returnValues[1]);
 }

}
</code></pre>

blocks|key|1647533|text|使用下面的Entry对象示例：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1647534|public+Entry<A,B>+methodname(arg)
{
.......

return+new+AbstractMap.simpleEntry<A,B>(instanceOfA,instanceOfB);
}|code-block|syntax|javascript|1647535|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|$]]

Use of following Entry object
Example :

<pre><code>public Entry&lt;A,B&gt; methodname(arg)
{
.......

return new AbstractMap.simpleEntry&lt;A,B&gt;(instanceOfA,instanceOfB);
}
</code></pre>

blocks|key|1432680|text|在C中，您可以通过将指针作为参数传递给结果的占位符来实现：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1432681|void+getShoeAndWaistSizes(int+*shoeSize,+int+*waistSize)+{
++++*shoeSize+=+36;
++++*waistSize+=+45;
}
...
int+shoeSize,+waistSize;
getShoeAndWaistSize(&shoeSize,+&waistSize);
int+i+=+shoeSize+%2B+waistSize;|code-block|syntax|javascript|1432682|让我们在Java中尝试类似的方法。|1432683|void+getShoeAndWaistSizes(List<Integer>+shoeSize,+List<Integer>+waistSize)+{
++++shoeSize.add(36);
++++waistSize.add(45);
}
...
List<Integer>+shoeSize+=+new+List<>();
List<Integer>+waistSize+=+new+List<>();
getShoeAndWaistSizes(shoeSize,+waistSize);
int+i+=+shoeSize.get(0)+%2B+waistSize.get(0);|1432684|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

In C, you would do it by passing pointers to placeholders for the results as arguments:

<pre><code>void getShoeAndWaistSizes(int *shoeSize, int *waistSize) {
 *shoeSize = 36;
 *waistSize = 45;
}
...
int shoeSize, waistSize;
getShoeAndWaistSize(&amp;shoeSize, &amp;waistSize);
int i = shoeSize + waistSize;
</code></pre>

Let's try something similar, in Java.

<pre><code>void getShoeAndWaistSizes(List&lt;Integer&gt; shoeSize, List&lt;Integer&gt; waistSize) {
 shoeSize.add(36);
 waistSize.add(45);
}
...
List&lt;Integer&gt; shoeSize = new List&lt;&gt;();
List&lt;Integer&gt; waistSize = new List&lt;&gt;();
getShoeAndWaistSizes(shoeSize, waistSize);
int i = shoeSize.get(0) + waistSize.get(0);
</code></pre>

blocks|key|1432742|text|如果您调用的方法是私有的，或者是从一个位置调用的，请尝试|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1432743|return+new+Object[]{value1,+value2};|code-block|syntax|javascript|1432744|调用者如下所示：|1432745|Object[]+temp=myMethod(parameters);
Type1+value1=(Type1)temp[0];++//For+code+clarity:+temp[0]+is+not+descriptive
Type2+value2=(Type2)temp[1];|1432746|David+Hanak的配对示例没有语法上的好处，并且被限制为两个值。|1432747|return+new+Pair<Type1,Type2>(value1,+value2);|1432748|调用者看起来像这样：|1432749|Pair<Type1,+Type2>+temp=myMethod(parameters);
Type1+value1=temp.a;++//For+code+clarity:+temp.a+is+not+descriptive
Type2+value2=temp.b;|1432750|entityMap^0|0|0|0|0|0|0|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]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

In the event the method you're calling is private, or called from one location, try

<pre><code>return new Object[]{value1, value2};
</code></pre>

The caller looks like:

<pre><code>Object[] temp=myMethod(parameters);
Type1 value1=(Type1)temp[0]; //For code clarity: temp[0] is not descriptive
Type2 value2=(Type2)temp[1];
</code></pre>

The Pair example by David Hanak has no syntactic benefit, and is limited to two values. 

<pre><code>return new Pair&lt;Type1,Type2&gt;(value1, value2);
</code></pre>

And the caller looks like:

<pre><code>Pair&lt;Type1, Type2&gt; temp=myMethod(parameters);
Type1 value1=temp.a; //For code clarity: temp.a is not descriptive
Type2 value2=temp.b;
</code></pre>

blocks|key|1647652|text|可以在动态语言(Python)中做一些像元组这样的事情|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1647653|public+class+Tuple+{
private+Object[]+multiReturns;

private+Tuple(Object...+multiReturns)+{
++++this.multiReturns+=+multiReturns;
}

public+static+Tuple+_t(Object...+multiReturns){
++++return+new+Tuple(multiReturns);
}

public+<T>+T+at(int+index,+Class<T>+someClass)+{
++++return+someClass.cast(multiReturns[index]);
}
}|code-block|syntax|javascript|1647654|并像这样使用|1647655|public+Tuple+returnMultiValues(){
+++return+Tuple._t(new+ArrayList(),new+HashMap())
}


Tuple+t+=+returnMultiValues();
ArrayList+list+=+t.at(0,ArrayList.class);|1647656|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Can do some thing like a tuple in dynamic language (Python)

<pre><code>public class Tuple {
private Object[] multiReturns;

private Tuple(Object... multiReturns) {
 this.multiReturns = multiReturns;
}

public static Tuple _t(Object... multiReturns){
 return new Tuple(multiReturns);
}

public &lt;T&gt; T at(int index, Class&lt;T&gt; someClass) {
 return someClass.cast(multiReturns[index]);
}
}
</code></pre>

and use like this

<pre><code>public Tuple returnMultiValues(){
 return Tuple._t(new ArrayList(),new HashMap())
}


Tuple t = returnMultiValues();
ArrayList list = t.at(0,ArrayList.class);
</code></pre>

blocks|key|1647689|text|将列表传递给您的方法并填充它，然后返回带有名称的字符串，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1647690|public+String+buildList(List<?>+list)+{
++++list.add(1);
++++list.add(2);
++++list.add(3);
++++return+"something,something,something,dark+side";
}|code-block|syntax|javascript|1647691|然后这样叫它：|1647692|List<?>+values+=+new+ArrayList<?>();
String+names+=+buildList(values);|1647693|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Pass a list to your method and populate it, then return the String with the names, like this:

<pre><code>public String buildList(List&lt;?&gt; list) {
 list.add(1);
 list.add(2);
 list.add(3);
 return "something,something,something,dark side";
}
</code></pre>

Then call it like this:

<pre><code>List&lt;?&gt; values = new ArrayList&lt;?&gt;();
String names = buildList(values);
</code></pre>

blocks|key|1432884|text|我遵循了与其他答案中描述的方法类似的方法，并根据我的需求进行了一些调整，基本上我创建了以下类(以防万一，一切都是Java)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1432885|public+class+Pair<L,+R>+{
++++final+L+left;
++++final+R+right;

++++public+Pair(L+left,+R+right)+{
++++++++this.left+=+left;
++++++++this.right+=+right;
++++}

++++public+<T>+T+get(Class<T>+param)+{
++++++++return+(T)+(param+==+this.left.getClass()+?+this.left+:+this.right);
++++}

++++public+static+<L,+R>+Pair<L,+R>+of(L+left,+R+right)+{
++++++++return+new+Pair<L,+R>(left,+right);
++++}
}|code-block|syntax|javascript|1432886|然后，我的需求很简单，在到达数据库的仓库类中，对于Get方法，我需要检查它是失败还是成功，如果成功，我需要处理返回的列表，如果失败，则停止执行并通知错误。|1432887|例如，我的方法是这样的：|1432888|public+Pair<ResultMessage,+List<Customer>>+getCustomers()+{
++++List<Customer>+list+=+new+ArrayList<Customer>();
++++try+{
++++/*
++++*+Do+some+work+to+get+the+list+of+Customers+from+the+DB
++++*+*/
++++}+catch+(SQLException+e)+{
++++++++return+Pair.of(
+++++++++++++++++++++++new+ResultMessage(e.getErrorCode(),+e.getMessage()),+//+Left+
+++++++++++++++++++++++null);++//+Right
++++}
++++return+Pair.of(
+++++++++++++++++++new+ResultMessage(0,+"SUCCESS"),+//+Left+
+++++++++++++++++++list);+//+Right
}|1432889|其中ResultMessage只是一个具有两个字段(代码/消息)的类，而Customer是具有来自DB的一组字段的任何类。|1432890|然后，为了检查结果，我只需执行以下操作：|1432891|void+doSomething(){
++++Pair<ResultMessage,+List<Customer>>+customerResult+=+_repository.getCustomers();
++++if+(customerResult.get(ResultMessage.class).getCode()+==+0)+{
++++++++List<Customer>+listOfCustomers+=+customerResult.get(List.class);
++++++++System.out.println("do+SOMETHING+with+the+list+;)+");
++++}else+{
++++++++System.out.println("Raised+Error...+do+nothing!");
++++}
}|1432892|entityMap^0|0|0|0|0|0|0|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]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

I followed a similar approach than the described in the other answers with a few tweaks based on the requirement I had, basically I created the following classes(Just in case, everything is Java):

<pre><code>public class Pair&lt;L, R&gt; {
 final L left;
 final R right;

 public Pair(L left, R right) {
 this.left = left;
 this.right = right;
 }

 public &lt;T&gt; T get(Class&lt;T&gt; param) {
 return (T) (param == this.left.getClass() ? this.left : this.right);
 }

 public static &lt;L, R&gt; Pair&lt;L, R&gt; of(L left, R right) {
 return new Pair&lt;L, R&gt;(left, right);
 }
}
</code></pre>

Then, my requirement was simple, in the repository Class that reaches the DB, for the Get Methods than retrieve data from the DB, I need to check if it failed or succeed, then, if succeed, I needed to play with the returning list, if failed, stop the execution and notify the error.

So, for example, my methods are like this:

<pre><code>public Pair&lt;ResultMessage, List&lt;Customer&gt;&gt; getCustomers() {
 List&lt;Customer&gt; list = new ArrayList&lt;Customer&gt;();
 try {
 /*
 * Do some work to get the list of Customers from the DB
 * */
 } catch (SQLException e) {
 return Pair.of(
 new ResultMessage(e.getErrorCode(), e.getMessage()), // Left 
 null); // Right
 }
 return Pair.of(
 new ResultMessage(0, "SUCCESS"), // Left 
 list); // Right
}
</code></pre>

Where ResultMessage is just a class with two fields (code/message) and Customer is any class with a bunch of fields that comes from the DB.

Then, to check the result I just do this:

<pre><code>void doSomething(){
 Pair&lt;ResultMessage, List&lt;Customer&gt;&gt; customerResult = _repository.getCustomers();
 if (customerResult.get(ResultMessage.class).getCode() == 0) {
 List&lt;Customer&gt; listOfCustomers = customerResult.get(List.class);
 System.out.println("do SOMETHING with the list ;) ");
 }else {
 System.out.println("Raised Error... do nothing!");
 }
}
</code></pre>

blocks|key|1647762|text|而在你的情况下，the+comment可能是一个很好的选择，在安卓中，你可以使用Pair+。简单地说|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1647763|return+new+Pair<>(yourList,+yourCommaSeparatedValues);|code-block|syntax|javascript|1647764|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/457629/how-to-return-multiple-objects-from-a-java-method#comment7726206_457629|1|https://developer.android.com/reference/android/util/Pair.html^0|14|4|8|B|0|14|5|1|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]|$9|10|A|11|1|12]]|E|$]]|$1|F|3|G|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]|S|$5|N|O|P|E|$Q|T]]]]

While in your case, <a href="https://stackoverflow.com/questions/457629/how-to-return-multiple-objects-from-a-java-method#comment7726206_457629">the comment</a> may be a good way to go, in Android, you can use <a href="https://developer.android.com/reference/android/util/Pair.html" rel="nofollow noreferrer"><code>Pair</code> </a>. Simply

<pre><code>return new Pair&lt;&gt;(yourList, yourCommaSeparatedValues);
</code></pre>

blocks|key|1647796|text|保持它的简单性，并为多结果情况创建一个类。此示例接受来自数据库助手getInfo的ArrayList和消息文本。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1647797|其中调用返回多个编码的值的例程：|1647798|multResult+res+=+mydb.getInfo();+|code-block|syntax|javascript|1647799|在例程getInfo中，您可以编写以下代码：|1647800|ArrayList<String>+list=+new+ArrayList<String>();
add+values+to+the+list...
return+new+multResult("the+message",+list);|1647801|并使用以下命令定义一个类multResult：|1647802|public+class+multResult+{
++++public+String+message;+//+or+create+a+getter+if+you+don't+like+public
++++public+ArrayList<String>+list;
++++multResult(String+m,+ArrayList<String>+l){
++++++++message+=+m;
++++++++list=+l;
}|1647803|}|1647804|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|11|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

Keep it simple and create a class for multiple result situation. This example accepts an ArrayList and a message text from a databasehelper getInfo.

Where you call the routine that returns multiple values you code:

<pre><code>multResult res = mydb.getInfo(); 
</code></pre>

In the routine getInfo you code:

<pre><code>ArrayList&lt;String&gt; list= new ArrayList&lt;String&gt;();
add values to the list...
return new multResult("the message", list);
</code></pre>

and define a class multResult with:

<pre><code>public class multResult {
 public String message; // or create a getter if you don't like public
 public ArrayList&lt;String&gt; list;
 multResult(String m, ArrayList&lt;String&gt; l){
 message = m;
 list= l;
}
</code></pre>

}

blocks|key|1647833|text|您可以使用HashMap<String,+Object>，如下所示|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1647834|public+HashMap<String,+Object>+yourMethod()
{

+++....+different+logic+here+

++HashMap<String,+Object>+returnHashMap+=+new+HashMap<String,+Object>();
++returnHashMap.put("objectA",+objectAValue);
++returnHashMap.put("myString",+myStringValue);
++returnHashMap.put("myBoolean",+myBooleanValue);

++return+returnHashMap;
}|code-block|syntax|javascript|1647835|然后，当在不同的作用域中调用该方法时，可以将每个对象转换回其初始类型：|1647836|//+call+the+method
HashMap<String,+Object>+resultMap+=+yourMethod();
++++++++++++++++
//+fetch+the+results+and+cast+them
ObjectA+objectA+=+(ObjectA)+resultMap.get("objectA");
String+myString+=+(String)+resultMap.get("myString");
Boolean+myBoolean+=+(Boolean)+resultMap.get("myBoolean");|1647837|entityMap^0|5|N|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

You can utilize a <code>HashMap&lt;String, Object&gt;</code> as follows
<pre><code>public HashMap&lt;String, Object&gt; yourMethod()
{

 .... different logic here 

 HashMap&lt;String, Object&gt; returnHashMap = new HashMap&lt;String, Object&gt;();
 returnHashMap.put(&quot;objectA&quot;, objectAValue);
 returnHashMap.put(&quot;myString&quot;, myStringValue);
 returnHashMap.put(&quot;myBoolean&quot;, myBooleanValue);

 return returnHashMap;
}
</code></pre>
Then when calling the method in a different scope, you can cast each object back to its initial type:
<pre><code>// call the method
HashMap&lt;String, Object&gt; resultMap = yourMethod();
 
// fetch the results and cast them
ObjectA objectA = (ObjectA) resultMap.get(&quot;objectA&quot;);
String myString = (String) resultMap.get(&quot;myString&quot;);
Boolean myBoolean = (Boolean) resultMap.get(&quot;myBoolean&quot;);
</code></pre>

I want to return two objects from a Java method and was wondering what could be a good way of doing so?

The possible ways I can think of are: return a <code>HashMap</code> (since the two Objects are related) or return an <code>ArrayList</code> of <code>Object</code> objects.

To be more precise, the two objects I want to return are (a) <code>List</code> of objects and (b) comma separated names of the same.

I want to return these two Objects from one method because I dont want to iterate through the list of objects to get the comma separated names (which I can do in the same loop in this method).

Somehow, returning a <code>HashMap</code> does not look a very elegant way of doing so.

How to return multiple objects from a Java method?

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我想从一个Java方法返回两个对象，我想知道有什么好方法可以做到这一点？我能想到的可能方法是:返回一个HashMap (因为这两个对象是相关的)或返回一个Object对象的ArrayList。更准确地说，我想返回的两个对象是(a)对象的List和(b)相同对象的逗号分隔名称。我想从一个方法返回这两个对象，因为我不想通过...

问如何从Java方法返回多个对象？
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