function ArrayList(){
    this.arr=[],
    this.size=function(){
        return this.arr.length;
    },
    this.add=function(){
        if(arguments.length==1){
            this.arr.push(arguments[0]);
        }else if(arguments.length>=2){
            var deleteItem=this.arr[arguments[0]];
            this.arr.splice(arguments[0],1,arguments[1],deleteItem)
        }
        return this;
    },
    this.get=function(index){
        return this.arr[index];
    },
    this.removeIndex=function(index){
        this.arr.splice(index,1);
    },
    this.removeObj=function(obj){
        this.removeIndex(this.indexOf(obj));
    },
    this.indexOf=function(obj){
        for(var i=0;i<this.arr.length;i++){
            if (this.arr[i]===obj) {
                return i;
            };
        }
        return -1;
    },
    this.isEmpty=function(){
        return this.arr.length==0;
    },
    this.clear=function(){
        this.arr=[];
    },
    this.contains=function(obj){
        return this.indexOf(obj)!=-1;
    }
 
  };