blocks|key|690409|text|查看键值对的简单方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|690410|Map<String,+Integer>+map+=+new+HashMap<>();
map.put("a",+1);
map.put("b",+2);
System.out.println(Arrays.asList(map));+//+method+1
System.out.println(Collections.singletonList(map));+//+method+2|code-block|syntax|javascript|690411|方法1和方法2都输出以下内容：|690412|[{b=2,+a=1}]|690413|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|$]]

A simple way to see the key value pairs:

<pre><code>Map&lt;String, Integer&gt; map = new HashMap&lt;&gt;();
map.put("a", 1);
map.put("b", 2);
System.out.println(Arrays.asList(map)); // method 1
System.out.println(Collections.singletonList(map)); // method 2
</code></pre>

Both method 1 and method 2 output this:

<pre><code>[{b=2, a=1}]
</code></pre>

blocks|key|906484|text|假设你有一个Map<KeyType,+ValueType>，你可以这样打印它：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|906485|for+(Map.Entry<KeyType,+ValueType>+entry+:+map.entrySet())+{
++++System.out.println(entry.getKey()%2B"+:+"%2Bentry.getValue());
}|code-block|syntax|javascript|906486|entityMap^0|6|N|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|$]]

Assuming you have a <code>Map&lt;KeyType, ValueType&gt;</code>, you can print it like this:

<pre><code>for (Map.Entry&lt;KeyType, ValueType&gt; entry : map.entrySet()) {
 System.out.println(entry.getKey()+" : "+entry.getValue());
}
</code></pre>

blocks|key|690308|text|要同时打印key和value，请使用以下命令：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|690309|for+(Object+objectName+:+example.keySet())+{
+++System.out.println(objectName);
+++System.out.println(example.get(objectName));
+}|code-block|syntax|javascript|690310|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|$]]

To print both key and value, use the following:

<pre><code>for (Object objectName : example.keySet()) {
 System.out.println(objectName);
 System.out.println(example.get(objectName));
 }
</code></pre>

blocks|key|690589|text|对我来说，这一句简单的话很管用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|690590|Arrays.toString(map.entrySet().toArray())|code-block|syntax|javascript|690591|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|$]]

For me this simple one line worked well:

<pre><code>Arrays.toString(map.entrySet().toArray())
</code></pre>

blocks|key|690225|text|您需要的是值集，而不是键集：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|690226|for+(TypeValue+name:+this.example.values())+{
++++++++System.out.println(name);
}|code-block|syntax|javascript|690227|你给出的代码甚至不能编译，这在以后的问题中可能值得一提--“似乎不能工作”有点含糊！|690228|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|$]]

You want the value set, not the key set:

<pre><code>for (TypeValue name: this.example.values()) {
 System.out.println(name);
}
</code></pre>

The code you give wouldn't even compile, which may be worth mentioning in future questions - "doesn't seem to work" is a bit vague!

blocks|key|906583|text|值得一提的是，使用BiConsumer和lambda函数的Java8方法：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|906584|BiConsumer<TypeKey,+TypeValue>+consumer+=+(o1,+o2)+->+
+++++++++++System.out.println(o1+%2B+",+"+%2B+o2);

example.forEach(consumer);|code-block|syntax|javascript|906585|假设您已经根据需要覆盖了这两种类型的toString方法。|906586|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/8/docs/api/java/util/function/BiConsumer.html^0|9|A|9|A|0|0|0|I|8|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|F|3|G|5|H|7|10|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|11|8|@$9|12|A|13|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

Worth mentioning Java 8 approach, using <a href="http://docs.oracle.com/javase/8/docs/api/java/util/function/BiConsumer.html" rel="noreferrer"><code>BiConsumer</code></a> and lambda functions:

<pre><code>BiConsumer&lt;TypeKey, TypeValue&gt; consumer = (o1, o2) -&gt; 
 System.out.println(o1 + ", " + o2);

example.forEach(consumer);
</code></pre>

Assuming that you've overridden <code>toString</code> method of the two types if needed.

blocks|key|690663|text|map.forEach((key,+value)+->+System.out.println(key+%2B+"+"+%2B+value));|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|690664|使用java+8特性|unstyled|690665|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>map.forEach((key, value) -&gt; System.out.println(key + " " + value));
</code></pre>

Using java 8 features

blocks|key|906668|text|Java8新特性forEach样式|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|906669|import+java.util.HashMap;

public+class+PrintMap+{
++++public+static+void+main(String[]+args)+{
++++++++HashMap<String,+Integer>+example+=+new+HashMap<>();
++++++++example.put("a",+1);
++++++++example.put("b",+2);
++++++++example.put("c",+3);
++++++++example.put("d",+5);

++++++++example.forEach((key,+value)+->+System.out.println(key+%2B+"+:+"+%2B+value));

//++++++Output:
//++++++a+:+1
//++++++b+:+2
//++++++c+:+3
//++++++d+:+5

++++}
}|code-block|syntax|javascript|906670|entityMap^0|8|7|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|$]]

Java 8 new feature <code>forEach</code> style 

<pre><code>import java.util.HashMap;

public class PrintMap {
 public static void main(String[] args) {
 HashMap&lt;String, Integer&gt; example = new HashMap&lt;&gt;();
 example.put("a", 1);
 example.put("b", 2);
 example.put("c", 3);
 example.put("d", 5);

 example.forEach((key, value) -&gt; System.out.println(key + " : " + value));

// Output:
// a : 1
// b : 2
// c : 3
// d : 5

 }
}
</code></pre>

blocks|key|690637|text|对于在HashMap中快速打印条目很有用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|690638|System.out.println(Arrays.toString(map.entrySet().toArray()));|code-block|syntax|javascript|690639|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|$]]

Useful to quickly print entries in a HashMap

<pre><code>System.out.println(Arrays.toString(map.entrySet().toArray()));
</code></pre>

blocks|key|690334|text|我使用了字符串映射(如果你正在使用字符串映射)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|690335|for+(Object+obj+:+dados.entrySet())+{
++++Map.Entry<String,+String>+entry+=+(Map.Entry)+obj;
++++System.out.print("Key:+"+%2B+entry.getKey());
++++System.out.println(",+Value:+"+%2B+entry.getValue());
}|code-block|syntax|javascript|690336|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|$]]

I did it using String map (if you're working with String Map).

<pre><code>for (Object obj : dados.entrySet()) {
 Map.Entry&lt;String, String&gt; entry = (Map.Entry) obj;
 System.out.print("Key: " + entry.getKey());
 System.out.println(", Value: " + entry.getValue());
}
</code></pre>

blocks|key|690546|text|如果映射将集合作为值保存，则其他答案需要额外的工作才能将它们转换为字符串，例如Arrays.deepToString(value.toArray())+(如果它是列表值的映射)，等等。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|690547|我经常遇到这些问题，并遇到使用ObjectMappers打印所有对象的通用函数。这在所有地方都很方便，特别是在实验的时候，我建议你选择这种方式。|690548|import+com.fasterxml.jackson.databind.ObjectMapper;
import+com.fasterxml.jackson.databind.SerializationFeature;

public+static+String+convertObjectAsString(Object+object)+{
++++String+s+=+"";
++++ObjectMapper+om+=+new+ObjectMapper();
++++try+{
++++++++om.enable(SerializationFeature.INDENT_OUTPUT);
++++++++s+=+om.writeValueAsString(object);
++++}+catch+(Exception+e)+{
++++++++log.error("error+converting+object+to+string+-+"+%2B+e);
++++}
++++return+s;
}|code-block|syntax|javascript|690549|entityMap^0|13|10|0|F|D|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|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|U|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

If the map holds a collection as value, the other answers require additional effort to convert them as strings, such as <code>Arrays.deepToString(value.toArray())</code> (if its a map of list values), etc.

I faced these issues quite often and came across the generic function to print all objects using <code>ObjectMappers</code>. This is quite handy at all the places, especially during experimenting things, and I would recommend you to choose this way.

<pre><code>import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

public static String convertObjectAsString(Object object) {
 String s = "";
 ObjectMapper om = new ObjectMapper();
 try {
 om.enable(SerializationFeature.INDENT_OUTPUT);
 s = om.writeValueAsString(object);
 } catch (Exception e) {
 log.error("error converting object to string - " + e);
 }
 return s;
}
</code></pre>

blocks|key|690701|text|使用java+8打印地图|type|unstyled|depth|inlineStyleRanges|entityRanges|data|690702|Map<Long,+String>+productIdAndTypeMapping+=+new+LinkedHashMap<>();
productIdAndTypeMapping.forEach((k,+v)+->+log.info("Product+Type+Key:+"+%2B+k+%2B+":+Value:+"+%2B+v));|code-block|syntax|javascript|690703|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|$]]

Print a Map using java 8
<pre><code>Map&lt;Long, String&gt; productIdAndTypeMapping = new LinkedHashMap&lt;&gt;();
productIdAndTypeMapping.forEach((k, v) -&gt; log.info(&quot;Product Type Key: &quot; + k + &quot;: Value: &quot; + v));
</code></pre>

blocks|key|906699|text|您可以使用Entry类轻松读取HashMap。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|906700|for(Map.Entry<TypeKey,+TypeKey>+temp+:+example.entrySet()){
++++System.out.println(temp.getValue());+//+Or+something+as+per+temp+defination.+can+be+used
}|code-block|syntax|javascript|906701|entityMap^0|5|5|F|7|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

You can use <code>Entry</code> class to read <code>HashMap</code> easily.

<pre><code>for(Map.Entry&lt;TypeKey, TypeKey&gt; temp : example.entrySet()){
 System.out.println(temp.getValue()); // Or something as per temp defination. can be used
}
</code></pre>

I have a <code>HashMap</code>:

<pre><code>private HashMap&lt;TypeKey, TypeValue&gt; example = new HashMap&lt;TypeKey, TypeValue&gt;();
</code></pre>

Now I would like to run through all the values and print them.

I wrote this:

<pre><code>for (TypeValue name : this.example.keySet()) {
 System.out.println(name);
}
</code></pre>

It doesn't seem to work.

What is the problem?

EDIT:
Another question: Is this collection zero based? I mean if it has 1 key and value will the size be 0 or 1?

Printing HashMap In Java

我有一台HashMapprivate HashMap<TypeKey, TypeValue> example = new HashMap<TypeKey, TypeValue>();现在我想遍历所有的值并打印它们。我写了以下内容：for (TypeValue name : this.example.keySet()) { System.out.println(name);}它似乎不起作用。有

问用Java打印HashMap
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