Java中的HashMap, Hashtable,TreeMap, LinkedHashMap

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stackoverflow

实例说明：

HashMap

public class Test {    public static void main(String[] args){        Map<String,String> hashmap = new HashMap<String,String>();        hashmap.put("name","range");        hashmap.put("age","25");        hashmap.put("sex","female");        hashmap.put("nationality","PR China");        hashmap.put("education","MD");        hashmap.put(null,null);        hashmap.put(null,"test");        hashmap.put("test",null);        Set<Map.Entry<String,String>> entryset = hashmap.entrySet();        for(Map.Entry<String,String> each : entryset){            System.out.println(each.getKey()+":"+each.getValue());        }    }}

输出结果：

null:testeducation:MDnationality:PR Chinatest:nullsex:femalename:rangeage:25

TreeMap

public class Test {    public static void main(String[] args){        Map<String,String> hashmap = new TreeMap<String,String>();        hashmap.put("name","range");        hashmap.put("age","25");        hashmap.put("sex","female");        hashmap.put("nationality","PR China");        hashmap.put("education","MD");//        hashmap.put(null,null);//        hashmap.put(null,"test");        hashmap.put("test",null);        Set<Map.Entry<String,String>> entryset = hashmap.entrySet();        for(Map.Entry<String,String> each : entryset){            System.out.println(each.getKey()+":"+each.getValue());        }    }}

输出结果：

age:25education:MDname:rangenationality:PR Chinasex:femaletest:null

LinkedHashMap

public class Test {    public static void main(String[] args){        Map<String,String> hashmap = new LinkedHashMap<String,String>();        hashmap.put("name","range");        hashmap.put("age","25");        hashmap.put("sex","female");        hashmap.put("nationality","PR China");        hashmap.put("education","MD");        hashmap.put(null,null);        hashmap.put(null,"test");        hashmap.put("test",null);        Set<Map.Entry<String,String>> entryset = hashmap.entrySet();        for(Map.Entry<String,String> each : entryset){            System.out.println(each.getKey()+":"+each.getValue());        }    }}

输出结果：

name:rangeage:25sex:femalenationality:PR Chinaeducation:MDnull:testtest:null

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