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//导入List接口和ArrayList实现类import java.util.List;import java.util.ArrayList;publicclassTest{publicstaticvoid main(String args []){ArrayList<String> arrayList =newArrayList<String>();//向arrayList当中添加对象 arrayList.add("a"); arrayList.add("b"); arrayList.add("c"); arrayList.add("d");//移除对象 arrayList.remove(1);//输出数组中的对象，调用arrayList.size()可以知道arranList的长度for(int i =0; i < arrayList.size(); i++){String s = arrayList.get(i);System.out.println(s);}}}
//导入接口和实现类，set接口是collection接口的子接口import java.util.Set;import java.util.HashSet;publicclassTest{publicstaticvoid main(String args []){//生成一个HashSet对象，再向上转型为Set类型//HashSet<String> hashSet = new HashSet<String>();//Set<String> set = HashSet;//等同于下面这行代码Set<String>set=newHashSet<String>(); boolean b1 =set.isEmpty();System.out.println(b1);set.add("a");set.add("b");set.add("c");set.add("d");set.add("c"); boolean b2 =set.isEmpty();System.out.println(b2);int i =set.size();System.out.println("clean之前set对象的长度是"+ i);set.remove("a");int j =set.size();System.out.println("remove之后set对象的长度是"+ j);set.clear();int k =set.size();System.out.println("clean之后set对象的长度是"+ k);}}
//导入接口和实现类，set接口是collection接口的子接口import java.util.Set;import java.util.HashSet;import java.util.Iterator;publicclassTest{publicstaticvoid main(String args []){//HashSet<String> hashSet = new HashSet<String>();//Set<String> set = HashSet;//Iterator <-- Collection <-- Set <-- HashSet// <-- List <-- ArrayListSet<String>set=newHashSet<String>();set.add("a");set.add("b");set.add("c");set.add("d");set.add("c");//调用Set对象的Iterator方法，会生成一个迭代器对象，该对象用于遍历整个SetIterator<String> it =set.iterator();while(it.hasNext()){String s = it.next();System.out.println(s);}}}import java.util.Map;import java.util.HashMap;publicclassTest{publicstaticvoid main(String args []){HashMap<String,String> hashMap =newHashMap<String,String>();//向上转型为Map类型Map<String,String>map= hashMap;//可以使用Map的put方法，向映射当中存放数据map.put("1","a");map.put("2","b");map.put("3","c");map.put("4","d");map.put("3","e");//使用size()方法，来得到map的长度int i =map.size();System.out.println(i);//根据键来取值String s =map.get("3");System.out.println(s);}}标签：
原文地址：http://www.cnblogs.com/arroneve/p/5815473.html
