ArrayList的用法

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直接看代码，不解释了，需要注意的就是方法。

import java.util.ArrayList;import java.util.Iterator;public class Test {    public static void main(String[] args) {        //instance        ArrayList list  = new ArrayList();        //public boolean add(E e)        list.add("a");        list.add("b");        list.add("c");        list.add("d");        //public void add(int index,E element)        list.add(0,"A");        //public E get(int index)        System.out.println("first element is: "+list.get(0));        //public boolean remove(@Nullable java.lang.Object o)        list.remove("c");        //public int size()        System.out.println("list size is: "+list.size());        //public boolean contains(java.lang.Object o)        System.out.println("list if contains 'c': "+list.contains("c"));        //public E set(int index,E element)        list.set(1,"e");        //Iterator        for (Iterator iter = list.iterator(); iter.hasNext();){            System.out.println("element is: "+iter.next());        }        //public java.lang.Object[] toArray()        Object[] array = list.toArray();        for(Object elem:array){            System.out.println("array =>"+elem);        }        /*        *public <T> T[] toArray(@NotNull T[] a)        *different from toArray()        */        String[] arr = (String[])list.toArray(new String[0]);        for(String elem:arr){            System.out.println("arr=>"+elem);        }        //public void clear()        list.clear();        //public boolean isEmpty()        System.out.println("list is empty:"+list.isEmpty());    }}

运行结果如下：

first element is: Alist size is: 4list if contains 'c': falseelement is: Aelement is: eelement is: belement is: darray =>Aarray =>earray =>barray =>darr=>Aarr=>earr=>barr=>dlist is empty:true

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