java - 检查对象以确保它不为空

Question

我正在尝试检查以确保我正在创建的对象不为空，目前我有

 import java.util.Scanner;
 import java.util.InputMismatchException;

public class Driver2 {

public static void main(String args[]){
    Scanner keyboard= new Scanner(System.in);

    //creates cars
    Vehicle aCar= new Vehicle();
    Vehicle bCar= new Vehicle();
    Vehicle cCar= new Vehicle();

    //creates trucks
    Truck aTruck= new Truck();
    Truck bTruck= new Truck();
    Truck cTruck= new Truck();

    //data checks
    boolean aCarCheck= false;
    boolean bCarCheck= false;
    boolean cCarCheck= false;
    boolean nameCheck1= false;
    boolean nameCheck1Full= false;
    boolean nameCheck2= false;
    boolean nameCheck2Full = false;
    boolean nameCheck3= false;
    boolean nameCheck3Full= false;
    boolean aTruckCheck= false;
    boolean bTruckCheck= false;
    boolean cTruckCheck= false;

    while(!nameCheck1Full){

    System.out.println("Enter first persons name");
    Person owner1= new Person(keyboard.next());
    aCar.setOwner(owner1);
    if (owner1==null){
        System.out.println("Please enter a name!");
        nameCheck1Full=false;

}else{
    nameCheck1Full=true;
}

    System.out.println("You entered: " + aCar.getOwner());

    while(!nameCheck2Full){
        System.out.println("Please enter second persons name");
        System.out.println("Please enter the same name for person 2 as person 1");
        Person owner2= new Person(keyboard.next());
        bCar.setOwner(owner2);
        if (bCar.equals(bCar))
        nameCheck2Full=true;
    }
}
}
}

我一直在寻找，似乎找不到适合我的好解决方案

我可能已经走了，因为这就是这个项目的一切，我非常接近放弃，但需要完成这个

标签： javanull

Answer 1

您检查 null 与：

if (myObject == null) ...

有时你真正想做的是检查空值：

String myValue = ...
if (myValue == null || "".equals(myValue)) ...