帶有switch語句的效率，Java
[英]Efficieny with switch Statements, Java
問題描述
最近，我開發了一個程序，要求用戶輸入年齡（年，月和日）。
收到輸入后，它必須進行計算和打印
a）以秒為單位的年齡（totalAgeInSecs）和
b）剩余的秒數。 b將基於以秒為單位的平均壽命(avgLifeSpan = 250000000000l. So secondsLeft = avgLifeSpan - totalAgeInSecs) 。
無論如何，為了簡單起見，我能夠使程序能夠使用（switch）語句來工作，而不必編寫一堆if / else語句，但是我覺得這樣做的結果是，我最終寫了重復的行， d不必重復計算或打印語句。
我知道有些類和數組可以與循環結合使用，但是為了簡單起見和邏輯理解，我沒有用它們來理解“英語”這個項目的無骨骨骼和邏輯。 哈哈。
無論如何，請查看下面的代碼，讓我知道您對如何簡化重復性代碼或實現此目的的更好方法的想法。 謝謝。
import java.util.*;
public class AgeInSeconds {
static Scanner kbd = new Scanner(System.in);
public static void main(String[] args) {
int totalNumDays, daysInMonth, daysToHours;
int yrsToDays,minsInHr, secsInMin;
long timeRemaining, avgLifeSecs;
System.out.println("Enter your age in years months and days: ");
System.out.print("Years: ");
int years = kbd.nextInt();
System.out.print("Months: ");
int months = kbd.nextInt();
System.out.print("Days: ");
int days = kbd.nextInt();
yrsToDays = years * 365;
avgLifeSecs = 2500000000l;
switch (months){
case 1:
daysInMonth = 31;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
break;
case 2:
daysInMonth = 59;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
break;
case 3:
daysInMonth = 90;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
break;
case 4:
daysInMonth = 120;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
break;
case 5:
daysInMonth = 151;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
break;
case 6:
daysInMonth = 181;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
break;
case 7:
daysInMonth = 212;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
break;
case 8:
daysInMonth = 243;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
break;
case 9:
daysInMonth = 273;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
break;
case 10:
daysInMonth = 304;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
break;
case 11:
daysInMonth = 334;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
break;
case 12:
daysInMonth = 365;
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
default:
}
kbd.close();
}
}
在以下情況下為輸出：年= 24，月= 5，天= 8。
Enter your age in years months and days:
Years: 24
Months: 5
Days: 8
You have been alive for 770,601,600 seconds.
The average human life is 2,500,000,000 seconds.
You have 1,729,398,400 seconds.
2 個解決方案
解決方案1
2 2015-09-28 08:14:33
要正確計算用戶的存活天數，您應該首先根據提供的數據和今天的日期計算其生日。 例如：
- 用戶的年齡為1個月，當前日期為2015年9月28日，因此該用戶出生於2015年8月28日，年齡為31天。
- 用戶的年齡為1個月，當前日期為2015年3月2日，因此該用戶出生於2015年2月2日，年齡為28天。
之后，您可以計算秒數差異。 Java API中有准備好的類和方法來執行這些步驟。 最簡單的是使用Java 8 Time API：
import java.time.LocalDateTime;
import java.time.Period;
import java.time.temporal.ChronoUnit;
import java.util.Scanner;
public class AgeInSeconds {
public static void main(String[] args) {
try (Scanner kbd = new Scanner(System.in)) {
System.out.println("Enter your age in years months and days: ");
System.out.print("Years: ");
int years = kbd.nextInt();
System.out.print("Months: ");
int months = kbd.nextInt();
System.out.print("Days: ");
int days = kbd.nextInt();
Period period = Period.of(years, months, days);
LocalDateTime now = LocalDateTime.now();
LocalDateTime birthDate = now.minus(period);
long seconds = birthDate.until(now, ChronoUnit.SECONDS);
long avgLifeSecs = 2500000000l;
long timeRemaining = avgLifeSecs - seconds;
System.out.printf("You have been alive for %,d seconds.\n", seconds);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
}
}
}
我在這里不解決統計問題。 要計算估計的剩余壽命（假設我是普通人），您應該平均比我死的人的壽命。
解決方案2
0 2015-09-28 08:01:16
您的整數daysInMonth將轉移通過switch語句。 因此，您只需在switch語句之后使用重復代碼即可。
經驗法則：當重復代碼時，將其放在自己的方法中，或者合並代碼，以便只需要在一個位置調用它。
import java.util.*;
public class AgeInSeconds {
static Scanner kbd = new Scanner(System.in);
public static void main(String[] args) {
int totalNumDays, daysInMonth, daysToHours;
int yrsToDays,minsInHr, secsInMin;
long timeRemaining, avgLifeSecs;
System.out.println("Enter your age in years months and days: ");
System.out.print("Years: ");
int years = kbd.nextInt();
System.out.print("Months: ");
int months = kbd.nextInt();
System.out.print("Days: ");
int days = kbd.nextInt();
yrsToDays = years * 365;
avgLifeSecs = 2500000000l;
switch (months){
case 1:
daysInMonth = 31;
break;
case 2:
daysInMonth = 59;
break;
case 3:
daysInMonth = 90;
break;
case 4:
daysInMonth = 120;
break;
case 5:
daysInMonth = 151;
break;
case 6:
daysInMonth = 181;
break;
case 7:
daysInMonth = 212;
break;
case 8:
daysInMonth = 243;
break;
case 9:
daysInMonth = 273;
break;
case 10:
daysInMonth = 304;
break;
case 11:
daysInMonth = 334;
break;
case 12:
daysInMonth = 365;
break;
default:
daysInMonth = 0;
}
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
kbd.close();
}
}
上面是代碼的“快速而骯臟的”解決方案，因此您可以看到如何通過switch語句傳遞變量。
更好的做法是使用模運算符檢查它是奇數還是偶數，如果不是第二個月，則給出正確的值。
import java.util.*;
public class AgeInSeconds {
static Scanner kbd = new Scanner(System.in);
public static void main(String[] args) {
int totalNumDays, daysInMonth, daysToHours;
int yrsToDays,minsInHr, secsInMin;
long timeRemaining, avgLifeSecs;
System.out.println("Enter your age in years months and days: ");
System.out.print("Years: ");
int years = kbd.nextInt();
System.out.print("Months: ");
int months = kbd.nextInt();
System.out.print("Days: ");
int days = kbd.nextInt();
yrsToDays = years * 365;
avgLifeSecs = 2500000000l;
/** predifine with 0 so we always have a value **/
daysInMonth = 0;
/** Our months here. Please consider using calendar **/
int[] legaldays = {31,28,31,30,31,30,31,31,30,31,30,31};
/** Looping through all months **/
for(i=0;i<legaldays.length;i++) {
/** check if we didn't pass our max limit **/
if(i+1 > daysInMonth) {
break;
}
/** add the days to our tally **/
daysInMonth += legaldays[i];
}
totalNumDays = yrsToDays + daysInMonth + days;
daysToHours = totalNumDays * 24;
minsInHr = daysToHours * 60;
secsInMin = minsInHr * 60;
timeRemaining = avgLifeSecs - secsInMin;
System.out.printf("You have been alive for %,d seconds.\n", secsInMin);
System.out.printf("The average human life is %,d seconds.\n", avgLifeSecs);
System.out.printf("You have %,d seconds.\n", timeRemaining);
kbd.close();
}
}
查看評論以了解我如何進行改進。 通過循環，您不必為硬編碼幾個月內的值而煩惱，它為您提供了一定的靈活性。 為了獲得更可靠的天數而不是硬編碼，我建議您查看特定年份一個月中的天數，以便靈活使用leap年。
只要有可能，就不要對無形或動態數據值進行硬編碼，而是嘗試准確地推導它們。 眾所周知，日期很難保持秩序。
將語句切換為 If 語句 - JAVA
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