Java使用joining合并字符串技巧

List<String> words = Arrays.asList("Java", "Python", "C++");

// 使用逗号分隔
String result1 = words.stream()
    .collect(Collectors.joining(", "));
System.out.println(result1); // 输出：Java, Python, C++

// 添加分号分隔，并加中括号包围
String result2 = words.stream()
    .collect(Collectors.joining("; ", "[", "]"));
System.out.println(result2); // 输出：[Java; Python; C++]

List<String> listWithNull = Arrays.asList("Apple", null, "Banana", "", "Cherry");

String safeJoin = listWithNull.stream()
    .filter(s -> s != null && !s.trim().isEmpty()) // 过滤 null 和空字符串
    .collect(Collectors.joining(", "));

System.out.println(safeJoin); // 输出：Apple, Banana, Cherry

class Person {
    String name;
    Person(String name) { this.name = name; }
    String getName() { return name; }
}

List<Person> people = Arrays.asList(new Person("Alice"), new Person("Bob"));

String names = people.stream()
    .map(Person::getName)
    .collect(Collectors.joining(" | "));

System.out.println(names); // 输出：Alice | Bob