类集框架

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ArrayList:

public class Test {
public static void main (String args[]){
  ArrayList<String> arrayList = new ArrayList<String>();
  arrayList.add("a");
  arrayList.add("b");
  arrayList.add("c");
  for(int i=0; i<arrayList.size(); i++){
   String s = arrayList.get(i);
   System.out.println(s);
  }
}
}

Set：

五种基本方法：boolean add(Object o) , void clear(), boolean isEmpty(),remove(Object o), int size()

public class Test {
public static void main (String args[]){
  Set<String> set = new HashSet<String>();
  boolean b1 = set.isEmpty();
  System.out.println(b1);
  set.add("a");
  set.add("b");
  set.add("c");
  set.remove("a");
  set.clear();
  int i = set.size();
  System.out.println(i);
}
}

循环获得set里的值：

public class Test {
public static void main (String args[]){
  Set<String> set = new HashSet<String>();
  set.add("a");
  set.add("b");
  set.add("c");
  Iterator<String> it = set.iterator();
  while(it.hasNext()){
   String s = it.next();
   System.out.println(s);
  }
}
}

Map:

public class Test {
public static void main (String args[]){
HashMap<String, String> hashMap = new HashMap<String, String>();
Map<String, String> map = hashMap;
map.put("1", "a");
map.put("2", "b");
String s = map.get("1");
System.out.println(s);
}
}