NSMutableArray *array=[NSMutableArray arrayWithObject:@"1"];
//添加元素
    [array addObject:@"2"];
    [array addObject:@"3"];
    NSLog(@"%@",array);

 //删除对象
    [array removeObject:@"2"];

  //删除最后一个元素
    [array removeLastObject];

    //删除全部元素
    [array removeAllObjects];

void arrayMemory(){

    NSMutableArray *array=[NSMutableArray array];
    Student *stu=[Student studentWithAge:10];
    Student *stu2=[Student studentWithAge:20];
    Student *stu3=[Student studentWithAge:30];
    
    
    //添加元素的时候会做一次retain操作，计数器+1
    [array addObject:stu];
    
   // NSLog(@"stu:%zi",[stu retainCount]);
    //对被删除的元素做一次release操作，计数器-1
    [array removeObject:stu];
     //  NSLog(@"stu:%zi",[stu retainCount]);
    
    //当数组被释放的时候，会对所有的元素都做一次release操作
}

void arrayReplace(){

    NSMutableArray *array=[NSMutableArray arrayWithObjects:@"1",@"2",@"3",nil];
    [array replaceObjectAtIndex:1 withObject:@"4"];
    NSLog(@"%@",array);

}

//排序方法
void arraySort(){
    NSMutableArray *array=[NSMutableArray arrayWithObjects:@"1",@"3",@"2",nil];
    //因为这个是可变数组，所以不需要返回值。
    [array sortUsingSelector:@selector(compare:)];
    NSLog(@"%@",array);

}