Java HashMap转TreeMap

Map<String, String> testMap = new HashMap<String, String>();

testMap.put("1", "3");

testMap.put("3", "4");

testMap.put("2", "1");

testMap.put("4", "2");

for (String key : testMap.keySet()) {

    System.out.println(key + "=>" + testMap.get(key));

}

System.out.println("========================");

Map<String, String> testMap2 = new TreeMap<String, String>(testMap);

for (String key : testMap2.keySet()) {

    System.out.println(key + "=>" + testMap2.get(key));

}

3=>4

2=>1

1=>3

4=>2

========================

1=>3

2=>1

3=>4

4=>2

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