java ArrayList详解及其方法
Java中的ArrayList
ArrayList是一个由Collection框架中的List接口实现的类。
ArrayList实现List接口，而List接口是Collection接口的子接口，因此最终ArrayList可以包含List和Collection接口的方法。
1）Collection接口方法：
booleanadd(Objecto)
booleanaddAll(Collectionc)
booleanremove(Objecto)
booleanremoveAll(Collectionc)
booleanretainAll(Collectionc)
voidclear()
booleanisEmpty()
intsize()
booleancontains(Objecto)
booleancontainsAll(Collectionc)
Object[]toArray()
Iteratoriterator()
例：
我们将从下面给出的示例中了解Collection接口方法的工作方式：
import java.util.*;
class CollectionMethods{
public static void main(String[] args){
ArrayList al = new ArrayList();
System.out.println("boolean add(Object o) : Add an object in ArrayList");
al.add(10);
al.add(20);
al.add(30);
al.add(40);
al.add(50);
System.out.println("Updated ArrayList is : " + al);
System.out.println("boolean addAll(Collection c) : Add Collection in ArrayList");
al.addAll(al);
System.out.println("Updated ArrayList is : " + al);
System.out.println("boolean contains(Object o) : it returns true if element contain");
al.contains(10);
System.out.println("Updated ArrayList is : " + al);
System.out.println("boolean containsAll(Collection c) : it returns true if collection contain");
al.containsAll(al);
System.out.println("Updated ArrayList is : " + al);
System.out.println("boolean toArray() : collection object convert into array");
Object[] values = al.toArray();
for(int i=0;i<values.length;++i)
System.out.println("Display in Array form : " + values[i]);
System.out.println("boolean iterator() : it iterates collection object");
Iterator it = al.iterator();
while(it.hasNext())
System.out.println("Iterating ArrayList : " + it.next());
}
}输出结果
D:\Java Articles>java CollectionMethods boolean add(Object o) : Add an object in ArrayList Updated ArrayList is : [10, 20, 30, 40, 50] boolean addAll(Collection c) : Add Collection in ArrayList Updated ArrayList is : [10, 20, 30, 40, 50, 10, 20, 30, 40, 50] boolean contains(Object o) : it returns true if element contain Updated ArrayList is : [10, 20, 30, 40, 50, 10, 20, 30, 40, 50] boolean containsAll(Collection c) : it returns true if collection contain Updated ArrayList is : [10, 20, 30, 40, 50, 10, 20, 30, 40, 50] boolean toArray() : collection object convert into array Display in Array form : 10 Display in Array form : 20 Display in Array form : 30 Display in Array form : 40 Display in Array form : 50 Display in Array form : 10 Display in Array form : 20 Display in Array form : 30 Display in Array form : 40 Display in Array form : 50 boolean iterator() : it iterates collection object Iterating ArrayList : 10 Iterating ArrayList : 20 Iterating ArrayList : 30 Iterating ArrayList : 40 Iterating ArrayList : 50 Iterating ArrayList : 10 Iterating ArrayList : 20 Iterating ArrayList : 30 Iterating ArrayList : 40 Iterating ArrayList : 50
2）列表接口方法
booleanadd(intindex,Objecto)
booleanaddAll(intindex,Collectionc)
Objectremove(intindex)
Objectget(intindex)
Objectset(intindex,Objectnew)
intindexOf(Objecto)
intlastIndexOf(Objecto)
ListIteratorlistiterator()
示例
我们将从以下示例中了解List接口方法的工作方式：
import java.util.*;
class ListMethods{
public static void main(String[] args){
ArrayList al = new ArrayList();
LinkedList ll = new LinkedList();
ll.add(10);
ll.add(20);
ll.add(30);
ll.add(40);
ll.add(50);
al.add(10);
al.add(20);
al.add(30);
al.add(40);
al.add(50);
System.out.println("Basic arraylist are :"+al);
System.out.println(" add(int index,Object o): It adds an object to a specified index" );
al.add(2,25);
System.out.println("Updated arraylist are :"+al);
System.out.println(" addAll(int index,Collection c): It adds collection to a specified index" );
al.addAll(6,al);
System.out.println("Updated arraylist are :"+al);
System.out.println(" get(int index): It returns object from a particular index" );
int value = (int)al.get(2);
System.out.println("Return value of :"+value);
System.out.println(" indexOf(Object o): It returns an index of a particular object" );
int index = (int)al.indexOf(25);
System.out.println("Return index of a particular object :"+index);
System.out.println(" lastIndexOf(Object o): It returns a last occurrence index of a particular object" );
int last_index = (int)al.lastIndexOf(50);
System.out.println("Return index of a particular object :"+last_index);
System.out.println(" listIterator(): It iterates list object" );
ListIterator li = ll.listIterator();
while(li.hasNext())
System.out.println("Display objects in list form :"+li.next());
}
}输出结果
D:\Java Articles>java ListMethods Basic arraylist are :[10, 20, 30, 40, 50] add(int index,Object o): It adds an object to a specified index Updated arraylist are :[10, 20, 25, 30, 40, 50] addAll(int index,Collection c): It adds collection to a specified index Updated arraylist are :[10, 20, 25, 30, 40, 50, 10, 20, 25, 30, 40, 50] get(int index): It returns object from a particular index Return value of :25 indexOf(Object o): It returns an index of a particular object Return index of a particular object :2 lastIndexOf(Object o): It returns a last occurrence index of a particular object Return index of a particular object :11 listIterator(): It iterates list object Display objects in list form :10 Display objects in list form :20 Display objects in list form :30 Display objects in list form :40 Display objects in list form :50