What are the methods of traversing Map in Java?

1. Create an Enum

public enum FactoryStatus {
    BAD(0,"ou"),
    GOOD(1,"yeah");

    private int status;
    private String description;
    FactoryStatus(int status, String description){
        this.status=status;
        this.description=description;
    }

    public int getStatus() {
        return status;
    }

    public String getDescription(){
        return description;
    }
}

This Enum is used as the value of the Map.

2. Start traversing

Method 1

Set set = map.keySet();
for (Object o : set) {
    System.out.println(o+""+map.get(o));
}

Traverse through the key set collection, and then use the key to get the value of the map. This method is more commonly used.

Method 2

Set set = map.keySet();
Iterator iterator = set.iterator();
while (iterator.hasNext()){
    Object next = iterator.next();
    System.out.println("key为："+next+",value为："+map.get(next));
}

Traverse the key set collection in the form of an iterator, and then use the key to get the value of the map.

Method 3

Set<Map.Entry<String, FactoryStatus>> entries = map.entrySet();
Iterator<Map.Entry<String, FactoryStatus>> iterator1 = entries.iterator();
while (iterator1.hasNext()){
    Map.Entry<String, FactoryStatus> next = iterator1.next();
    System.out.println("方法三的key为："+next.getKey()+",value为："+next.getValue());
}

Traverse the key-value pairs of the Map in the form of an iterator, and then obtain the values ​​of k and v through the .getKey() and .getValue() methods.

Method 4

Collection<FactoryStatus> values = map.values();
for (FactoryStatus value : values) {
    System.out.println("方法四的value为："+value);
}

This method directly takes out the value of the map and puts it in the collection, and then loops through v.

Method 5

Set<Map.Entry<String, FactoryStatus>> entries = map.entrySet();
for (Map.Entry<String, FactoryStatus> entry : entries) {
    System.out.println("方法五的key为："+entry.getKey()+",value为："+entry.getValue());
}

Obtain all key-value pairs through the foreach loop and traverse all k and v. This method is theoretically recommended, especially when the capacity is large.

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