List
实现了List接口的方法:
AbstractList, AbstractSequentialList, ArrayList, AttributeList, CopyOnWriteArrayList, LinkedList, RoleList, RoleUnresolvedList, Stack, Vector
解析
可以看到 List 继承了 Collection 接口.比起Collection而言List多了很多方法,同时还重写了Spliterator方法.以及默认实现了部分方法.
下面先看一看已经默认实现了的方法
replaceAll
可以看到,replaceAll的实现方式是:
- 传入一个UnaryOperator
- 调用this.listIterator();
- 如果 迭代器 有下一个元素
- 将下一个元素的值赋值为UnaryOperator.apply的结果
- 如果 没有
使用demo
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| public class Main {
public static void main(String[] args){
List list = new ArrayList<Integer>();
for(int i = 0; i < 10 ; i++){
list.add(i);
}
for(int i =0 ; i < list.size();i++){
System.out.print(list.get(i));
}
System.out.println();
list.replaceAll(new UnaryOperator<Integer>() {
@Override
public Integer apply(Integer integer) {
return integer <= 4 ? integer : 4;
}
});
for(int i =0 ; i < list.size();i++){
System.out.print(list.get(i));
}
System.out.println();
}
}
|
输出结果
用lambda表达式
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| list.replaceAll(o -> (Integer) o > 4? 4:o);
|
结果一样
sort
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| default void sort(Comparator<? extends E> c){
Object[] a = this.toArray();
Arrays.sort(a,(Comparator)c);
ListIterator<E> i = this.listIterator();
for (Object e : a){
i.next();
i.set((E)e );
}
}
``` java
public interface List<E> extends Collection<E> {
int size();
boolean isEmpty();
boolean contains(Object o);
Iterator<E> iterator();
Object[] toArray();
<T> T[] toArray(T[] a);
boolean add(E e);
boolean remove(Object o);
boolean containsAll(Collection<?> c);
boolean addAll(Collection<? extends E> c);
boolean addAll(int index, Collection<? extends E> c);
boolean removeAll(Collection<?> c);
boolean retainAll(Collection<?> c);
default void replaceAll(UnaryOperator<E> operator){
Objects.requireNonNull(operator);
final ListIterator<E> li = this.listIterator();
while( li.hasNext()){
li.set(operator.apply(li.next()));
}
}
default void sort(Comparator<? extends E> c){
Object[] a = this.toArray();
Arrays.sort(a,(Comparator)c);
ListIterator<E> i = this.listIterator();
for (Object e : a){
i.next();
i.set((E)e );
}
}
void clear();
boolean equals(Object o);
int hashCode();
E get(int index);
E set(int index, E element);
void add(int index, E element);
E remove(int index);
int indexOf(Object o);
int lastIndexOf(Object o);
ListIterator<E> listIterator();
ListIterator<E> listIterator(int index);
List<E> subList(int fromIndex, int toIndex);
@Override
default Spliterator<E> Spliterator(){
return Spliterators.spliterator(this,Spliterator.ORDERED);
}
}
|
- 先把List转换成数组
- 然后通过Arrays的静态方法传入数组和Comparator进行排序
- 获取迭代器,调用迭代器的next(),set()方法按序赋值
### Arrays
是一个工具类,包含了控制数组的各个方法