java-遍历集合

import java.security.AlgorithmConstraints;
import java.util.ArrayList;
import java.util.Iterator;
public class one {
public static void main(String[] args){
ArrayList a=new ArrayList();
boolean b = a.add(“b”);
// System.out.println(b);
//向集合加数据
a.add(“小红”);
a.add(0,“jack”);//向指定位置加数据
String collection = null;
a.add(collection);//将一个集合加到另一个集合里
a.remove(0);//移除数据
for(int i=0;i<a.size();i++)//遍历集合
{
System.out.println(a.get(i));
}
System.out.println(a.isEmpty());//判断数据是否为空
System.out.println(a.contains(“小明”));//判断是否包含’小明’
Object[] d = a.toArray();//把集合转换为数组
1 for(int i=0;i<a.toArray().length;i++)//遍历集合
{
System.out.println(a.get(i));
}
2 Iterator iterator=a.iterator();
System.out.println(iterator.next());
System.out.println(iterator.next());
System.out.println(iterator.next());
while(iterator.hasNext()){
System.out.println(iterator.next());
}
3 for(Object o:a){
System.out.println(o);
}
4 int[] array=new int[] {34,23,564,2,3,5,454};
for (int temp:array){
System.out.println(temp);
}
}
}