七种遍历Map的方法

小灰灰 2024-03-23 17:25 56阅读 0赞

#### 七种遍历Map的方法 ####

import java.util.HashMap;
    import java.util.Iterator;
    import java.util.Map;
    
    public class Wan {
        
        public static void main(String[] args) {
        
            Map<String,String> dataMap = new HashMap<>();
            dataMap.put("A","Abb");
            dataMap.put("B","Bcc");
            dataMap.put("C","Cdd");
    
    
            // 1. forEach+lambda
            dataMap.forEach((k,v)-> System.out.println(k+"->"+v));
    
            // 2. keySet+foreach
            for (String key: dataMap.keySet()){
        
                System.out.println(key+"->"+dataMap.get(key));
            }
    
            // 3. entry+stream
            dataMap.entrySet().stream().forEach(entry ->
                    System.out.println(entry.getKey()+"->"+entry.getValue())
            );
    
            // 4. stream并行处理
            dataMap.entrySet().stream().parallel().forEach(entry ->
                    System.out.println(entry.getKey()+"->"+entry.getValue())
            );
    
            // 5. foreach Map.EntrySet
            for (Map.Entry<String,String> item: dataMap.entrySet()) {
        
                System.out.println(item.getKey()+"->"+item.getValue());
            }
    
            // 6.迭代器+Map.Entry
            Iterator<Map.Entry<String,String>> item2 = dataMap.entrySet().iterator();
            while (item2.hasNext()){
        
                Map.Entry<String,String> next = item2.next();
                System.out.println(next.getKey()+"->"+next.getValue());
            }
    
            // 7. keyset+迭代器
            Iterator<String> item3 = dataMap.keySet().iterator();
            while (item3.hasNext()){
        
                String key = item3.next();
                System.out.println(key+"->"+dataMap.get(key));
            }
            
        }
    }