我需要編寫一個 Mobile 數(shù)組列表，執(zhí)行一些操作，例如添加、刪除、更新和顯示。然而，當談到對 arraylist 中的對象進行排序時，我有點困惑。我正在談?wù)摬⒖糷ttps://beginnersbook.com/2017/08/comparator-interface-in-java/在駕駛類中 //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貢獻1797條經(jīng)驗 獲得超6個贊
正如這段代碼
while (true) {永遠不會退出，此循環(huán)下面的代碼無法訪問
也許System.exit(0);應(yīng)該只是打破循環(huán)while。
breaka中的注釋switch不會打破while循環(huán)
千巷貓影
TA貢獻1829條經(jīng)驗 獲得超7個贊
將這些行放入 while 循環(huán)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您還可以使用java 8 及以上版本的可用來簡化比較操作。喜歡：
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貢獻1936條經(jīng)驗 獲得超7個贊
while永遠不會到達循環(huán)后的代碼。您需要編寫一些邏輯來跳出 while 循環(huán)。解決此問題的一種簡單方法是：
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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