Java和Python中PHP的foreach($array as $key => $value)等价写法

15 投票
8 回答
22936 浏览
提问于 2025-04-15 13:20

在PHP中,我们可以用一种叫做关联数组的方式来处理州名和它们的缩写,像这样:

<?php
    $stateArray = array(
        "ALABAMA"=>"AL",
        "ALASKA"=>"AK",
        // etc...
        "WYOMING"=>"WY"
    );

    foreach ($stateArray as $stateName => $stateAbbreviation){
        print "The abbreviation for $stateName is $stateAbbreviation.\n\n";
    }
?>

输出结果(保持了键的顺序):

The abbreviation for ALABAMA is AL.

The abbreviation for ALASKA is AK.

The abbreviation for WYOMING is WY.

补充说明:注意,在PHP版本的输出中,数组元素的顺序是被保留的。而在Java中使用HashMap时,元素的顺序是不固定的。Python中的字典也是如此。

那么在Java和Python中是怎么做到的呢?我只找到了一些方法是根据键来获取值,比如Python的:

stateDict = {
    "ALASKA": "AK",
    "WYOMING": "WY",
}

for key in stateDict:
    value = stateDict[key]

补充说明:根据大家的回答,这是我在Python中的解决方案,

# a list of two-tuples
stateList = [
    ('ALABAMA', 'AL'),
    ('ALASKA', 'AK'),
    ('WISCONSIN', 'WI'),
    ('WYOMING', 'WY'),
]

for name, abbreviation in stateList:
    print name, abbreviation

输出结果:

ALABAMA AL
ALASKA AK
WISCONSIN WI
WYOMING WY

这正是所需要的结果。

8 个回答

2

在Python中,有一种叫做有序字典的东西,它在Python 2.7(还没发布)和Python 3.1中可以使用。这个有序字典的名字叫OrderedDict。

6

在Java中,如果你想使用关联数组,可以用Map。

import java.util.*;

class Foo
{
    public static void main(String[] args)
    {
        Map<String, String> stateMap = new HashMap<String, String>();
        stateMap.put("ALABAMA", "AL");
        stateMap.put("ALASKA", "AK");
        // ...
        stateMap.put("WYOMING", "WY");

        for (Map.Entry<String, String> state : stateMap.entrySet()) {
             System.out.printf(
                "The abbreviation for %s is %s%n",
                state.getKey(),
                state.getValue()
            );
        }
    }
}
34

在Python中:

for key, value in stateDict.items(): # .iteritems() in Python 2.x
    print "The abbreviation for %s is %s." % (key, value)

在Java中:

Map<String,String> stateDict;

for (Map.Entry<String,String> e : stateDict.entrySet())
    System.out.println("The abbreviation for " + e.getKey() + " is " + e.getValue() + ".");

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