java - 按字母顺序排列

Question

我是 Java 新手，我正在尝试按字母顺序排列术语数组列表。 (术语定义为 char 和 int)(例如 {Term('Z',4),Term('C',3),Term('Q',2) ...} )

我的代码如下:

    public Term nextElement()
{
    Term max = terms.get(0);
    char maxtest = max.getElement();
    for (int i = 1; i < terms.size(); i++){
        Term tester = terms.get(i);
        char maxtest2 = tester.getElement();
        if (maxtest2 > maxtest) {
            tester = max;
        }
    }
    return max;
}

为什么这不起作用？我该如何做到这一点？我的 arrayList 称为 term，填充类型为 Term

Answer 1

您的这行代码有问题。您的类(class)不是 Comparable 的类型那么，根据哪个属性或标准compareTo()方法将 compare这两个对象？？？

   res = maxtest.compareTo(maxtest2); //Your maxtest object is not Comparable Type.

您必须需要上课 Term比较型。并且，重写方法 compareTo()根据您的需要。

您没有提及您的类的变量或结构 Term 。所以，我假设你的类(class)有这样的结构。

public class Term implements Comparable<Term> {
    private Character alpha;
   private int number;
   //getter and setters +Constructors as you specified
   ....
    ....
     ...
      .....
//  Now Set a criteria to sort is the Alphanumeric.
    @Override
    public int compareTo(Term prm_obj) {
        if (prm_obj.getAlpha() > this.alpha) {
            return 1;
        } else if (prm_obj.getAlpha() < this.alpha) {
            return -1;

        } else {
            return 0;
        }

    }

现在你的类(class)变成了comparable类型。所以您可以申请Collections.sort(Collection obj)这会自动sort你的ArrayList<Term> .

这里我为此编写了一个演示。

public static void main(String... args){

    List<Term> obj_listTerm = new ArrayList<>();
     //add all the data you given in question
    obj_listTerm .add(new Term('Z', 4)); 
    obj_listTerm .add(new Term('Q', 2));
    obj_listTerm .add(new Term('c', 3));

    // print without Sorting your Term ArrayList.
    System.out.println("This is the list unsorted: " + myTermList);
    // Sort Using Collections.sort() Method.

    Collections.sort(myTermList);

    // After applying sort() you may see your Sorted ArrayList.
    System.out.println("This is the list SORTED: " + myTermList);
}