Answer:
Step-by-step explanation:
The following code is written in Java and contains each of the methods requested working and performing the requested functions. 
class GasTank { 
 double amount = 0; 
 double capacity; 
 
 public void GasTank(double capacity) { 
 this.capacity = capacity; 
 } 
 
 public void addGas(double gasAmount) { 
 this.amount += gasAmount; 
 if (this.amount > this.capacity) { 
 this.amount = this.capacity; 
 } 
 } 
 
 public void useGas(double useGas) { 
 this.amount -= useGas; 
 if (this.amount < 0) { 
 this.amount = 0; 
 } 
 } 
 
 public boolean isEmpty() { 
 if (this.amount < 0.1) { 
 return true; 
 } else { 
 return false; 
 } 
 } 
 
 public boolean isFull() { 
 if (this.amount > (this.capacity - 0.1)) { 
 return true; 
 } else { 
 return false; 
 } 
 } 
 
 
 public double getGasLevel() { 
 return this.amount; 
 } 
 
 
}