优雅判空

1.Optional

orElse
orElseThrow
ifPresent
ofNullable()
of()
map()

2.优雅使用optional进行为null的if-else判断

Optional.ofNullable(rule).map(r -> {
	context.getProcessModel().setNotifyMethods(notifyMethods);
	context.getProcessModel().setNotifyEnable(rule.getNeedNotification());
	return context;
}).orElseGet(() -> {
	context.setNeedBreak(true);
	return context;
});

3.Optional 的几个用法

if-or-else

Optional<String> optionalValue = Optional.ofNullable(getValue());

optionalValue.ifPresent(value -> System.out.println("Value is present: " + value));

String result = optionalValue.orElse("Default Value");
System.out.println("Result: " + result);

map和orElse

Optional<String> optionalValue = Optional.ofNullable(getValue());

String transformedValue = optionalValue
    .map(value -> "Transformed " + value)
    .orElse("Default Value");

System.out.println("Transformed Value: " + transformedValue);

orElseGet和orElseThrow

Optional<String> optionalValue = Optional.ofNullable(getValue());

String result = optionalValue.orElseGet(() -> "Computed Default Value");
System.out.println("Result: " + result);

try {
    String value = optionalValue.orElseThrow(() -> new IllegalArgumentException("Value is missing"));
    System.out.println("Value: " + value);
} catch (IllegalArgumentException e) {
    System.out.println(e.getMessage());
}

filter,符合条件链式执行

Optional<String> optionalValue = Optional.ofNullable(getValue());

optionalValue
    .filter(value -> value.startsWith("A"))
    .ifPresent(value -> System.out.println("Value starts with A: " + value));