Java中map的九种遍历方法-创新互联

1. 通过for和map.entrySet()遍历

public void ergodicMap(Mapmap){for(Map.Entryentry : map.entrySet()){System.out.println("Key:"+entry.getKey()+",Value:"+entry.getValue());
    }
}

2. 通过for，iterator和map.entrySet()遍历

public void ergodicMap(Mapmap){for(Iterator>entries = map.entrySet().iterator();entries.hasNext();){Map.Entryentry = entries.next();
        System.out.println("Key:"+entry.getKey()+",Value:"+entry.getValue());
    }
}

3. 通过while，Iterator和map.entrySet()遍历

public void ergodicMap(Mapmap){Iterator>entries = map.entrySet().iterator();
    while(entries.hasNext()){ Map.Entryentry = entries.next();
        System.out.println("Key:"+entry.getKey()+",Value:"+entry.getValue());
    }
}

4. 通过for和map.keySet()遍历

public void ergodicMap(Mapmap){for(Integer key : map.keySet()){System.out.println("Key:"+key+",Value:"+map.getKey());
    }
}

5. 通过for，Iterator和map.keySet()遍历

public void ergodicMap(Mapmap){for(Iteratorkey = map.keySet().iterator(); key.hasNext();){System.out.println("Key:"+key.next()+",Value:"+map.get(key.next()));
    }
}

6. 通过while，Iterator和map.keySet()遍历

public void ergodicMap(Mapmap){Iteratorkey = map.keySet().iterator();
    while(key.hasNext()){System.out.println("Key:"+key.next()+",Value:"+map.get(key.next()));
    }
}

7. 通过map.forEach()遍历

JDK中的forEach方法，使用率比较高。

public void ergodicMap(Mapmap){map.forEach((key,value) ->{   System.out.println("Key:"+key+",Value:"+value);
    })
}

8. Stream遍历

public void ergodicMap(Mapmap){long sum = map.entrySet().stream().mapToLong(e ->e.getKey() + e.getValue)).sum();
    System.out.println(sum);
}

9. parallelStream遍历

public void ergodicMap(Mapmap){long sum = map.entrySet().parallelStream().mapToLong(e ->e.getKey() + e.getValue)).sum();
   System.out.println(sum);
}

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