JAVA中关于Collection接口方法使用源程序问题

来源：百度知道 编辑：UC知道 时间：2024/09/22 16:42:16
import java.util.*;
class ContainerDemo
{
public static void main(String[] args){
Collection c1 = new ArrayList(25);
c1.add(new String("one"));
c1.add(new String("two"));
String s = "three";
c1.add(s);
for (int i = 0; i<c1.size(); i++)
{System.out.println(c1.get(i));
}
Object[] array = c1.toArray();
String[] str = (String[])c1.toArray(new String[0]);
System.out.println(Arrays.toString(str));
Collection c2 = new ArrayList(2);
c2.add(new String("four"));
c2.add(new String("five"));
c1.addAll(c2);
for (int i = 0; i<c1.size(); i++ )
{System.out.println(c1.get(i));
}
Collection c3 = new ArrayList(2);
c3.add(new String("two"));
c3.add(new String("five"));
c1.removeAll(c3);
for (int i = 0; i<c1.size(); i++)
{System.out.println(c1.get(

因为你用的是Collection型的引用变量 这个接口里没有实现 get方法所以你就不能用get来获取数据~~

要想获取 Collection型里保存的数据可以用叠代器
把
for (int i = 0; i<c1.size(); i++)
{System.out.println(c1.get(i));
}
该成
Iterator it =c1.iterator();
while(it.hasNext)
{
System.out.println(it.next)
}

Collection c1 = new ArrayList(25); 是不是这个原因呢，分配空间太大了呢

import java.util.*;

class ContainerDemo {
public static void main(String[] args) {
Collection<String> c1 = new ArrayList<String>(25);
Iterator<String> iterator;
c1.add(new String("one"));
c1.add(new String("two"));
String s = "three";
c1.add(s);
iterator=c1.iterator();
while(iterator.hasNext()){
System.out.println(iterator.next());
}
Object[] array = c1.toArray();
String[] str = (String[]) c1.toArray(new String[0]);
System.out.println(Arrays.toString(str));
Col