java大量的if else和switch类型的优化
java大量的if else和switch类型的优化
1. 使用策略模式
2. 使用责任链模式
3. 使用模版模式【枚举类】
案例1
如下方法：
public String transferNumber(int number) {
int base = 10000; // 1万
if (number <= base) {
return String.valueOf(number);
} else if (number < base * 100) {
return String.valueOf(number / base) + "万+";
} else if (number < base * 1000) {
return String.valueOf(number / base / 100) + "百万+";
} else {
return String.valueOf(number / base / 1000) + "千万+";
}
}
使用责任链模式
/**
* 责任链模式
*/
public interface MsgProcesser {
boolean match(int msg);
String processor(int msg);
}
public static class Processor implements MsgProcesser{
@Override
public boolean match(int msg) {
return msg < 10000;
}
@Override
public String processor(int msg) {
return String.valueOf(msg);
}
}
public static class WProcessor implements MsgProcesser{
@Override
public boolean match(int msg) {
return msg < 10000 * 100;
}
@Override
public String processor(int msg) {
return msg / 10000 + "万+";
}
}
public static class ProcessChain {
int index = 0;
List<MsgProcesser> processers = new ArrayList<>();
public ProcessChain add(MsgProcesser p) {
processers.add(p);
return this;
}
public String process(int msg) {
if(index == processers.size()) {
return "";
}
MsgProcesser proccess = processers.get(index);
if (proccess.match(msg)) {
return proccess.processor(msg);
}
index++;
return process(msg);
}
}
使用策略模式
/**
* 策略模式 1
*/
public interface Strategy {
String processor(int msg);
}
private static Map<IntRange, Strategy> rangeStrategyMap = new HashMap<>();
static {
rangeStrategyMap.put(new IntRange(0, 9999), String::valueOf);
rangeStrategyMap.put(new IntRange(10000, 10000 * 100 - 1), msg -> msg / 10000 + "万+");
rangeStrategyMap.put(new IntRange(10000 * 100, 10000 * 1000 - 1), msg -> msg / 10000 / 100 + "百万+");
rangeStrategyMap.put(new IntRange(10000 * 1000, Integer.MAX_VALUE), msg -> msg / 10000 / 1000 + "千万+");
}
public static Map<IntRange, Strategy> getRangeStrategyMap() {
return rangeStrategyMap;
}
/**
* 策略模式 2
*/
private static RangeMap<Integer, Strategy> rangeMap = TreeRangeMap.create();
static {
rangeMap.put(Range.closedOpen(0, 10000), String::valueOf);
rangeMap.put(Range.closedOpen(10000, 10000 * 100), msg -> msg / 10000 + "万+");
rangeMap.put(Range.closedOpen(10000 * 100, 10000 * 1000), msg -> msg / 10000 / 100 + "百万+");
rangeMap.put(Range.closedOpen(10000 * 1000, Integer.MAX_VALUE), msg -> msg / 10000 / 1000 + "千万+");
}
public static RangeMap<Integer, Strategy> getRangeMap() {
return rangeMap;
}
案例2
考虑下面的方法：
// Monday（星期一）、Tuesday（星期二）、Wednesday（星期三）、
// Thursday（星期四）、Friday（星期五）、Saturday（星期六）、Sunday（星期日）。
public String transferWeek(int day) {
switch (day) {
case 0:
return "Sunday";
case 1:
return "Monday";
case 2:
return "Tuesday";
case 3:
return "Wednesday";
case 4:
return "Thursday";
case 5:
return "Friday";
case 6:
return "Saturday";
default:
return "";
}
}
使用模版模式【枚举类】
public enum Week {
DEFAULT(-1) {
@Override
public String getWeekDay() {
return "";
}
},
SUN(0) {
@Override
public String getWeekDay() {
return "Sunday";
}
},
Mon(1) {
@Override
public String getWeekDay() {
return "Sunday";
}
},
TUE(2) {
@Override
public String getWeekDay() {
return "Tuesday";
}
},
WED(3) {
@Override
public String getWeekDay() {
return "Wednesday";
}
},
THU(4) {
@Override
public String getWeekDay() {
return "Thursday";
}
},
FRI(5) {
@Override
public String getWeekDay() {
return "Friday";
}
},
SAT(6) {
@Override
public String getWeekDay() {
return "Saturday";
}
},
;
private final int day;
public static Week valueOf(int day) {
for(Week week : Week.values()) {
if (!week.equals(Week.DEFAULT) && week.getDay() == day) {
return week;
}
}
return Week.DEFAULT;
}
public int getDay() {
return day;
}
public abstract String getWeekDay();
Week(int day) {
this.day = day;
}
}
代码
public class LGauva {
/**
* 责任链模式
*/
public interface MsgProcesser {
boolean match(int msg);
String processor(int msg);
}
public static class Processor implements MsgProcesser{
@Override
public boolean match(int msg) {
return msg < 10000;
}
@Override
public String processor(int msg) {
return String.valueOf(msg);
}
}
public static class WProcessor implements MsgProcesser{
@Override
public boolean match(int msg) {
return msg < 10000 * 100;
}
@Override
public String processor(int msg) {
return msg / 10000 + "万+";
}
}
public static class ProcessChain {
int index = 0;
List<MsgProcesser> processers = new ArrayList<>();
public ProcessChain add(MsgProcesser p) {
processers.add(p);
return this;
}
public String process(int msg) {
if(index == processers.size()) {
return "";
}
MsgProcesser proccess = processers.get(index);
if (proccess.match(msg)) {
return proccess.processor(msg);
}
index++;
return process(msg);
}
}
/**
* 策略模式 1
*/
public interface Strategy {
String processor(int msg);
}
private static Map<IntRange, Strategy> rangeStrategyMap = new HashMap<>();
static {
rangeStrategyMap.put(new IntRange(0, 9999), String::valueOf);
rangeStrategyMap.put(new IntRange(10000, 10000 * 100 - 1), msg -> msg / 10000 + "万+");
rangeStrategyMap.put(new IntRange(10000 * 100, 10000 * 1000 - 1), msg -> msg / 10000 / 100 + "百万+");
rangeStrategyMap.put(new IntRange(10000 * 1000, Integer.MAX_VALUE), msg -> msg / 10000 / 1000 + "千万+");
}
public static Map<IntRange, Strategy> getRangeStrategyMap() {
return rangeStrategyMap;
}
/**
* 策略模式 2
*/
private static RangeMap<Integer, Strategy> rangeMap = TreeRangeMap.create();
static {
rangeMap.put(Range.closedOpen(0, 10000), String::valueOf);
rangeMap.put(Range.closedOpen(10000, 10000 * 100), msg -> msg / 10000 + "万+");
rangeMap.put(Range.closedOpen(10000 * 100, 10000 * 1000), msg -> msg / 10000 / 100 + "百万+");
rangeMap.put(Range.closedOpen(10000 * 1000, Integer.MAX_VALUE), msg -> msg / 10000 / 1000 + "千万+");
}
public static RangeMap<Integer, Strategy> getRangeMap() {
return rangeMap;
}
public String transferNumber(int number) {
int base = 10000; // 1万
if (number <= base) {
return String.valueOf(number);
} else if (number < base * 100) {
return String.valueOf(number / base) + "万+";
} else if (number < base * 1000) {
return String.valueOf(number / base / 100) + "百万+";
} else {
return String.valueOf(number / base / 1000) + "千万+";
}
}
// Monday（星期一）、Tuesday（星期二）、Wednesday（星期三）、
// Thursday（星期四）、Friday（星期五）、Saturday（星期六）、Sunday（星期日）。
public String transferWeek(int day) {
switch (day) {
case 0:
return "Sunday";
case 1:
return "Monday";
case 2:
return "Tuesday";
case 3:
return "Wednesday";
case 4:
return "Thursday";
case 5:
return "Friday";
case 6:
return "Saturday";
default:
return "";
}
}
public enum Week {
DEFAULT(-1) {
@Override
public String getWeekDay() {
return "";
}
},
SUN(0) {
@Override
public String getWeekDay() {
return "Sunday";
}
},
Mon(1) {
@Override
public String getWeekDay() {
return "Sunday";
}
},
TUE(2) {
@Override
public String getWeekDay() {
return "Tuesday";
}
},
WED(3) {
@Override
public String getWeekDay() {
return "Wednesday";
}
},
THU(4) {
@Override
public String getWeekDay() {
return "Thursday";
}
},
FRI(5) {
@Override
public String getWeekDay() {
return "Friday";
}
},
SAT(6) {
@Override
public String getWeekDay() {
return "Saturday";
}
},
;
private final int day;
public static Week valueOf(int day) {
for(Week week : Week.values()) {
if (!week.equals(Week.DEFAULT) && week.getDay() == day) {
return week;
}
}
return Week.DEFAULT;
}
public int getDay() {
return day;
}
public abstract String getWeekDay();
Week(int day) {
this.day = day;
}
}
public static void main(String[] args) {
LGauva lGauva = new LGauva();
// 原始方法
System.out.println(lGauva.transferNumber(2));
System.out.println(lGauva.transferNumber(2000));
System.out.println(lGauva.transferNumber(20000));
System.out.println(lGauva.transferNumber(20000 * 100));
System.out.println(lGauva.transferNumber(20000 * 1000));
System.out.println(lGauva.transferNumber(20000 * 10000));
// 责任链
ProcessChain chain = new ProcessChain();
chain.add(new Processor());
chain.add(new WProcessor());
System.out.println(chain.process(20000));
int num = 20000 * 201;
// 策略1
Map<IntRange, Strategy> rangeStrategyMap = LGauva.getRangeStrategyMap();
Optional<Strategy> first = rangeStrategyMap.entrySet().stream()
.filter(entry -> entry.getKey().containsInteger(num))
.map(Map.Entry::getValue)
.findFirst();
String processor = first.orElse(String::valueOf).processor(num);
System.out.println(processor);
// 策略2
RangeMap<Integer, Strategy> rangeMap = LGauva.getRangeMap();
Strategy strategy = rangeMap.get(num);
if (strategy == null) {
strategy = String::valueOf;
}
System.out.println(strategy.processor(num));
// 使用模版模式【枚举类】
System.out.println(lGauva.transferWeek(0));
System.out.println(lGauva.transferWeek(6));
System.out.println(LGauva.Week.valueOf(0).getWeekDay());
System.out.println(LGauva.Week.valueOf(6).getWeekDay());
}
}