import java.util.HashMap; import java.util.LinkedHashMap; import java.util.Map; import java.util.TreeMap; public class Test { public static void main(String[] args) { Map tree = new TreeMap(); Map linked = new LinkedHashMap(); Map hash = new HashMap(); System.out.println("tree :"+buildMap(tree)); System.out.println("link :"+buildMap(linked)); System.out.println("hash :"+buildMap(hash)); } private static Map buildMap(Map map){ map.put("0", "a"); map.put("e", "b"); map.put("4", "s"); map.put("3", "c"); return map; } }
输出结果:
Java代码 tree :{0=a, 3=c, 4=s, e=b} link :{0=a, e=b, 4=s, 3=c} hash :{3=c, 0=a, 4=s, e=b}
由此可见:
HashMap是按照HashCode 排序,莫名其妙的顺序。
TreeMap是按照自身的顺序排序,比如数字的话,按照数字升序,ascII等。
LinkedHashMap是按照先进先出的顺序。