flex 中ArrayCollection筛选的问题

Question

function GetBlueLineData(value:String):void
{
var obj1:Object=new Object();
obj1["x7"]=RMS_MIN;
obj1["y7"]=value;
tchVoltageRealValueAArray.addItem(obj1);
var obj2:Object=new Object();
obj2["x7"]=BlueValueArray[BlueValueArray.length-1].x1;
obj2["y7"]=value;
if(RMS_MIN<BlueValueArray[BlueValueArray.length-1].x1)
{

for (var ssIndex:Number=RMS_MIN;ssIndex<BlueValueArray[BlueValueArray.length-1].x1;ssIndex++)
var ojb3:Object=new Object();
ojb3["x7"]=ssIndex;
ojb3["y7"]=value;

                    tchVoltageRealValueAArray.addItem(ojb3);

                }

                  tchVoltageRealValueAArray.addItem(obj2);
                  tchVoltageRealValue._dp=tchVoltageRealValueAArray;

}

怎么在方法体内先检查tchVoltageRealValueAArray是否有obj1["x7"],obj1["y7"].....