我需要编写一个 Mobile 数组列表，执行一些操作，例如添加、删除、更新和显示。然而，当谈到对 arraylist 中的对象进行排序时，我有点困惑。我正在谈论并参考https://beginnersbook.com/2017/08/comparator-interface-in-java/在驾驶类中 //Create an arraylist of Mobile ArrayList<Mobile> themobile = new ArrayList<>(); Scanner input = new Scanner(System.in); System.out.println("Welcome to Mobile"); System.out.println("Please select a number in the following: "); while (true) { //A list of options System.out.println("1. Diplay the next mobile."); System.out.println("2. Display the previous mobile."); System.out.println("3. Add a new mobile."); System.out.println("4. Remove a new mobile"); System.out.println("5. Update a mobile."); System.out.println("0. Exit"); //prompt user input int choice = input.nextInt(); switch(choice) { case 1: //displayNext(themobile); break; case 2: //displayPrevious(themobile); break; case 3: addMobile(themobile); break; case 4: removeMobile(themobile); break; case 5: updateMobile(themobile); break; case 0: System.out.println("Thank you for using a Mobile arraylist"); System.exit(0); } } Collections.sort((themobile, new MobileByBrandName()); System.out.println("Sorted by brand name" + themobile); Collections.sort(themobile, new MobileByMoNum()); System.out.println("Sorted by brand name" + themobile); Collections.sort(themobile, new MobileByInS()); System.out.println("Sorted by brand name" + themobile);}
3 回答
FFIVE
TA贡献1797条经验 获得超6个赞
正如这段代码
while (true) {永远不会退出，此循环下面的代码无法访问
也许System.exit(0);应该只是打破循环while。
breaka中的注释switch不会打破while循环
千巷猫影
TA贡献1829条经验 获得超7个赞
将这些行放入 while 循环中
Collections.sort((themobile, new MobileByBrandName());
System.out.println("Sorted by brand name" + themobile);
Collections.sort(themobile, new MobileByMoNum());
System.out.println("Sorted by brand name" + themobile);
Collections.sort(themobile, new MobileByInS());
System.out.println("Sorted by brand name" + themobile);
Comparator.comparing您还可以使用java 8 及以上版本的可用来简化比较操作。喜欢：
Comparator<Mobile> comparator = Comparator.comparing(new Function<Mobile,
@Override
public String apply(Mobile t) {
return t.getBrandName();
}
}).thenComparingInt(new ToIntFunction<Mobile>() {
@Override
public int applyAsInt(Mobile t) {
return t.getModelNumber();
}
}).thenComparingInt(new ToIntFunction<Mobile>() {
@Override
public int applyAsInt(Mobile t) {
return t.getInternalMemoryS();
}
});
Collections.sort(themobile, comparator);
LEATH
TA贡献1936条经验 获得超6个赞
while永远不会到达循环后的代码。您需要编写一些逻辑来跳出 while 循环。解决此问题的一种简单方法是：
int choice = -1;
while (choice != 0) {
choice = input.nextInt();
switch (choice) {
//...other cases
case 0:
System.out.println("Thank you for using a Mobile arraylist");
}
}
Collections.sort(...);
System.out.println(...);
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