Java if条件代码优化

Question

如果有任何其他简单的方法来优化/实现下面的代码，请帮助我。像home、bill、reg这样的变量可以是空字符串(“”)，也可以是空字符串(“”)，这取决于场景。

我的代码

public void helloWorld()
{
    List items=new ArrayList();
    items.add("1"); // dummy list
    String home=""; // can be null or empty
    String bill=null;  // can be null or empty
    String reg="";  // can be null or empty
    if(!items.isEmpty())
    {
        System.out.println("List is not null");
        if(home==null&&bill==null&&reg==null) 
        {
            System.out.println("home is null");
            System.out.println("bill is null");
            System.out.println("reg is null");
        }
        if(home==null&&bill==null&&reg!=null)
        {
            System.out.println("home is null");
            System.out.println("bill is null");
            System.out.println("reg is not null");
        }
        if(home==null&&bill!=null&&reg==null)
        {
            System.out.println("home is null");
            System.out.println("bill is not null");
            System.out.println("reg is null");
        }
        if(home==null&&bill!=null&&reg!=null)
        {
            System.out.println("home is null");
            System.out.println("bill is not null");
            System.out.println("reg is not null");
        }
        if(home!=null&&bill==null&&reg==null)
        {
            System.out.println("home is not null");
            System.out.println("bill is null");
            System.out.println("reg is null");
        }
        if(home!=null&&bill==null&&reg!=null)
        {
            System.out.println("home is not null");
            System.out.println("bill is null");
            System.out.println("reg is not null");
        }
        if(home!=null&&bill!=null&&reg==null)
        {
            System.out.println("home is not null");
            System.out.println("bill is not null");
            System.out.println("reg is null");
        }
        if(home!=null&&bill!=null&&reg!=null)
        {
            System.out.println("home is not null");
            System.out.println("bill is not null");
            System.out.println("reg is not null");
        }
    }
    else
    {
        System.out.println("List is null");
    }
}

请给我建议。提前谢谢。

Answer 1

只需分别检查home、bill和reg，因为它们彼此之间没有依赖关系。

public void helloWorld()
{
    List items=new ArrayList();
    items.add("1"); // dummy list
    String home=""; // can be null or empty
    String bill=null;  // can be null or empty
    String reg="";  // can be null or empty
    if(!items.isEmpty())
    {
        System.out.println("List is not null");
        System.out.println( home == null ? "home is null" : "home is not null" );
        System.out.println( bill == null ? "bill is null" : "bill is not null" );
        System.out.println( reg == null ? "reg is null" : "reg is not null" );

    }
    else
    {
        System.out.println("List is null");
    }
}

Answer 2

按照建议，只需检查每个变量，而不是列出所有排列。

    if(home==null) 
    {
        System.out.println("home is null");
    }
    else
    {
        System.out.println("home is not null");
    }
    if (bill==null)
    {
        System.out.println("bill is null");
    }
    else
    {
        System.out.println("bill is not null");
    }
    ...

Answer 3

 public void helloWorld() {
        List items = new ArrayList();
        items.add("1"); // dummy list
        String home = ""; // can be null or empty
        String bill = null;  // can be null or empty
        String reg = "";  // can be null or empty
        if (!items.isEmpty()) {
            System.out.println("List is not null");
            System.out.println("home is " + (StringUtils.isEmpty(home) ? "null" : "not null"));
            System.out.println("bill is " + (StringUtils.isEmpty(bill) ? "null" : "not null"));
            System.out.println("reg is " + (StringUtils.isEmpty(reg) ? "null" : "not null"));
        } else {
            System.out.println("List is null");
        }
    }

StringUtils.isEmpty()函数可用于检查空值和空值。