Optional 类如何优雅进行判空

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Optional 类如何优雅进行判空

2023-06-09 12:57| 来源: 网络整理| 查看: 265

1-判断对象为空

平常我们写空判断对象代码如下：

Student student = new Student("haha"); student = null; if (student != null) { String name = student.getName(); }

替换为 Optional 类型直进行判空，缺点直接判断代码依旧冗余。代码如下：

Optional studentB = Optional.ofNullable(student); if (studentB.isPresent()) { System.out.println(studentB.get().getName()); }

正确的做法建议使用流式操作，代码如下：

Optional.ofNullable(student).ifPresent(stu -> System.out.println(stu.getName())); 2-再比如获取获取对象中的类，为空就抛出异常

正常判断为空的写法

if (student != null) { if (student.getAddress() != null) { Address address = student.getAddress(); if (address.getCity() != null) { System.out.println(address.getCity()); } } } throw new RuntimeException("有空值");

正确的流式操作

Optional.ofNullable(student) .map(Student::getAddress) .map(Address::getCity) .orElseThrow(() -> new Exception("有空值")); 3-再比如获取名字为小马哥的学生，如果为空就返回一个新对象

平常的写法

public Student getStudent(Student student) throws RuntimeException { if (student != null) { String name = student.getName(); if ("xiaomage".equals(name)) { return student; } student = new Student(); student.setName("xiaomage"); return student; } else { student = new Student(); student.setName("xiaomage"); return student; } }

Optional 流方式操作写法

public Student getStudent2(Student student) { return Optional.ofNullable(student) .filter(stu -> "xiaomage".equals(stu.getName())) .orElseGet(() -> { Student studentNew = new Student(); studentNew.setName("xiaomage"); return studentNew; }); }

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Optional 类如何优雅进行判空

Optional 类如何优雅进行判空

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