java中两个浮点数进行比较

                double preErrorKey=1e-6; //1*10的-6次方即0.000001
                double key1=0.0000001d;
                double key2=0d;
//                System.out.println(key1==key2); //结果是flase
//                System.out.println(Math.abs(key1-key2)<preErrorKey);
                if(Math.abs(daohuoshuliang- shengoushuliang)<preErrorKey && (weidaohuoliang==0)){
                    caigouzhuangtai = "全部采购";