Map<String, String>，如何同时打印 "key string" 和 "value string"

Question

我是 Java 的新手，正在尝试学习地图的概念。

我想出了下面的代码。但是，我想同时打印出 "key String" 和 "value String"。

ProcessBuilder pb1 = new ProcessBuilder();
Map<String, String> mss1 = pb1.environment();
System.out.println(mss1.size());

for (String key: mss1.keySet()){
    System.out.println(key);
}

我只能找到只打印 "key String" 的方法。

Answer 1

在你的循环中，你有一个键，你可以用它从 Map:

中检索值

for (String key: mss1.keySet()) {
    System.out.println(key + ": " + mss1.get(key));
}

Answer 2

final Map<String, String> mss1 = new ProcessBuilder().environment();
mss1.entrySet()
        .stream()
        //depending on how you want to join K and V use different delimiter
        .map(entry -> 
        String.join(":", entry.getKey(),entry.getValue()))
        .forEach(System.out::println);

Answer 3

有多种方法可以实现这一点。这是三个。

    Map<String, String> map = new HashMap<String, String>();
    map.put("key1", "value1");
    map.put("key2", "value2");
    map.put("key3", "value3");

    System.out.println("using entrySet and toString");
    for (Entry<String, String> entry : map.entrySet()) {
        System.out.println(entry);
    }
    System.out.println();

    System.out.println("using entrySet and manual string creation");
    for (Entry<String, String> entry : map.entrySet()) {
        System.out.println(entry.getKey() + "=" + entry.getValue());
    }
    System.out.println();

    System.out.println("using keySet");
    for (String key : map.keySet()) {
        System.out.println(key + "=" + map.get(key));
    }
    System.out.println();

输出

using entrySet and toString
key1=value1
key2=value2
key3=value3

using entrySet and manual string creation
key1=value1
key2=value2
key3=value3

using keySet
key1=value1
key2=value2
key3=value3

Map<String, String>，如何同时打印 "key string" 和 "value string"

Map<String, String>, how to print both the "key string" and "value string" together

java

dictionary

key

输出