java 8 switch用法_Java14新特性：Switch表达式
Java 14正式发布switch表达式特性。在之前的两个 Java 版本Java12，Java13，switch特性只是预览版。
新的switch表达式有助于避免一些bug，因为它的表达和组合方式更容易编写。
switch新的表达式有两个特点：支持箭头表达式返回。
支持yied和return返回值。
Java 14之前switch语法：switch (day) {
case MONDAY:
case FRIDAY:
case SUNDAY:
System.out.println(6);
break;
case TUESDAY:
System.out.println(7);
break;
case THURSDAY:
case SATURDAY:
System.out.println(8);
break;
case WEDNESDAY:
System.out.println(9);
break;
}
Java 14 switch表达式switch (day) {
case MONDAY, FRIDAY, SUNDAY -> System.out.println(6);
case TUESDAY -> System.out.println(7);
case THURSDAY, SATURDAY -> System.out.println(8);
case WEDNESDAY -> System.out.println(9);
}
Java 14的switch表达式使用箭头表达时，不需要我们在每一个case后都加上break，减少我们出错的机会。
Java14之前switch语法返回值int numLetters;
switch (day) {
case MONDAY:
case FRIDAY:
case SUNDAY:
numLetters = 6;
break;
case TUESDAY:
numLetters = 7;
break;
case THURSDAY:
case SATURDAY:
numLetters = 8;
break;
case WEDNESDAY:
numLetters = 9;
break;
default:
throw new IllegalStateException("Wat: " + day);
}
它不支持返回值，需要通过一个中间变量来返回。
Java14 switch表达式返回值int numLetters = switch (day) {
case MONDAY, FRIDAY, SUNDAY -> 6;
case TUESDAY -> 7;
case THURSDAY, SATURDAY -> 8;
case WEDNESDAY -> 9;
};
Java 14 Switch表达式使用yield返回值int j = switch (day) {
case MONDAY -> 0;
case TUESDAY -> 1;
default -> {
int d = day.toString().length();
int result = f(d);
yield result;
}
};
Java 14正式发布switch表达式特性。在之前的两个 Java 版本Java12，Java13，switch特性只是预览版。 新的switch表达式有助于避免一些bug，因为它的表达和组合方式更容易编写。 switch新的表达式有两个特点：支持箭头表达式返回。 支持yied和return返回值。 Java 14之前switch语法：switch (day) { case MONDAY: case FRIDAY: case SUNDAY: System.out.println(6); break; case TUESDAY: System.out.println(7); break; case THURSDAY: case SATURDAY: System.out.println(8); break; case WEDNESDAY: System.out.println(9); break; } Java 14 switch表达式switch (day) { case MONDAY, FRIDAY, SUNDAY -> System.out.println(6); case TUESDAY -> System.out.println(7); case THURSDAY, SATURDAY -> System.out.println(8); case WEDNESDAY -> System.out.println(9); } Java 14的switch表达式使用箭头表达时，不需要我们在每一个case后都加上break，减少我们出错的机会。 Java14之前switch语法返回值int numLetters; switch (day) { case MONDAY: case FRIDAY: case SUNDAY: numLetters = 6; break; case TUESDAY: numLetters = 7; break; case THURSDAY: case SATURDAY: numLetters = 8; break; case WEDNESDAY: numLetters = 9; break; default: throw new IllegalStateException("Wat: " + day); } 它不支持返回值，需要通过一个中间变量来返回。 Java14 switch表达式返回值int numLetters = switch (day) { case MONDAY, FRIDAY, SUNDAY -> 6; case TUESDAY -> 7; case THURSDAY, SATURDAY -> 8; case WEDNESDAY -> 9; }; Java 14 Switch表达式使用yield返回值int j = switch (day) { case MONDAY -> 0; case TUESDAY -> 1; default -> { int d = day.toString().length(); int result = f(d); yield result; } };