我是Java新手,正在尝试按字母顺序排列术语的arrayList。(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;
}
为什么不起作用?我该如何做到这一点?我的arrayList被称为term,填充类型为Term
这行代码的问题。您的类不是Comparable
的类型,那么,在哪个属性或条件下,compareTo()
方法将compare
这两个对象???
res = maxtest.compareTo(maxtest2); //Your maxtest object is not Comparable Type.
您必须使类Term
成为Comparable类型。以及,根据需要覆盖方法compareTo()
。
您没有提到类Term
的变量或结构。所以,我假设你们班有这样的结构。
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;
}
}
现在你的课变成了comparable
类型。因此,您可以应用Collections.sort(Collection obj)
,它会自动为您的ArrayList<Term>
应用sort
。
在这里我写了一个演示。
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);
}
您可以使用Collection类并对您拥有的术语列表进行排序,您只需要使类term具有可比性
示例:
public class Term implements Comparable<Term> {
.....
// .....
// criteria to sort is the char
@Override
public int compareTo(Term o) {
if (o.getLetter()> this.letter) {
return 1;
} else if (o.getLetter() < this.letter) {
return -1;
} else {
return 0;
}
}
public static void main(String[] args) {
// test
List<Term> myTermList = new ArrayList<>();
myTermList.add(new Term('Z', 4));
myTermList.add(new Term('Q', 2));
myTermList.add(new Term('c', 3));
// check how the look like
System.out.println("This is the list unsorted: " + myTermList);
// now sort them
Collections.sort(myTermList);
// check how the look like
System.out.println("This is the list SORTED: " + myTermList);
}
编辑>
如果你不想实现可比性,那么修改这个:
res = maxtest.compareTo(maxtest2);
因为这是无效的,因为maxtest和maxtest2是基元而不是对象。。。
使用
res = Character.compare(maxtest, maxtest2);
然后使用结果来验证您的逻辑并做出决策:
if (res >1) {
System.out.println("bigger");
}else if (res<1) {
System.out.println("smaller");
}else {
System.out.println("same");
}