Question

我正在尝试创建生成唯一ID的方法。由于最终变量，我不能使用“return id ++”。还有其他选择吗？

public class Job {

        private final long id;
        private final int difficulty;
        private final String owner;

        public Job(int difficulty, String owner) {
            this.id = nextId();
            this.difficulty= difficulty;
            this.owner= owner;
        }

        public long nextId(){
            return id;
        }

我也试过java.util.UUID。可以使用最终变量生成唯一ID吗？

private final String id;
...
public String nextId(){
    id = UUID.randomUUID().toString();
    return id;

我真的很感激任何帮助

Answer 1

你需要两个变量：一个是静态的，它计算已经给出的ID，另一个是最后一个保存每个对象的ID。

public class Job {
    private static long nextId = 0L;

    private final long id;
    private final int difficulty;
    private final String owner;

    public Job(int difficulty, String owner) {
        this.id = nextId++;
        this.difficulty = difficulty;
        this.owner = owner;
    }

    // ...
}

如果这也需要在多线程环境中工作，则必须使用同步或原子操作（例如，AtomicLong）：

public class Job {
    private static AtomicLong nextId = new AtomicLong();

    private final long id;
    private final int difficulty;
    private final String owner;

    public Job(int difficulty, String owner) {
        this.id = nextId.getAndIncrement();
        this.difficulty = difficulty;
        this.owner = owner;
    }

    // ...
}

Java：如何生成唯一的长ID？

1 个答案: