java - 使用多个 if 值优化数组结果

Question

我想要 (yourItems.contains("Gin")) [显示 Gin 的所有饮料] + (yourItems.contains("Vodka")) [显示伏特加的所有饮料] 然后将包含这两种饮料的饮料移动到列表的顶部。

现在，只要我同时选择 Gin 和 Vodka 这两个值，我的应用程序就会崩溃

private List<Drinks> myDrinks = new ArrayList<Drinks>(); 
private ArrayList<String> yourItems;

...

    private void populateDrinkList() {

    if (yourItems.contains("Gin")){
     myDrinks.add(new Drinks("a"));
     myDrinks.add(new Drinks("b"));
     myDrinks.add(new Drinks("c"));
     myDrinks.add(new Drinks("d"));
     myDrinks.add(new Drinks("e"));

     if (yourItems.contains("Vodka")) {

           Drinks toMoveUp = new Drinks("e");
            while (myDrinks.indexOf(toMoveUp) != 0) {
            int i = myDrinks.indexOf(toMoveUp);
            Collections.swap(myDrinks, i, i-1 );
    }
     }

    }
    populateListView();
}

这是饮料类

public class Drinks {
String name = null;



    public Drinks(String name){
        this.name= name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
}
    }

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Answer 1

好的，我明白你的代码有什么问题了

在 Drinks 类中将此添加到您的代码中:

    @Override
public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((name == null) ? 0 : name.hashCode());
    return result;
}

@Override
public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    Drinks other = (Drinks) obj;
    if (name == null) {
        if (other.name != null)
            return false;
    } else if (!name.equals(other.name))
        return false;
    return true;
}

在另一个中保持这样:

private void populateDrinkList() {

     myDrinks.add(new Drinks("a"));
     myDrinks.add(new Drinks("b"));
     myDrinks.add(new Drinks("c"));
     myDrinks.add(new Drinks("d"));
     myDrinks.add(new Drinks("e"));

     if (yourItems.contains("Vodka") || yourItems.contains("Gin") ) {

           Drinks toMoveUp = new Drinks("e");
            while (myDrinks.indexOf(toMoveUp) != 0) {
            int i = myDrinks.indexOf(toMoveUp);
            Collections.swap(myDrinks, i, i-1 );
    }


    }
    populateListView();
}