如果你想要简短的、人类可读的id，并且只需要它们在每次JVM运行时是唯一的:

private static long idCounter = 0;

public static synchronized String createID()
{
    return String.valueOf(idCounter++);
}    

编辑:评论中建议的替代方案-这依赖于底层的线程安全“魔法”，但更可扩展，同样安全:

private static AtomicLong idCounter = new AtomicLong();

public static String createID()
{
    return String.valueOf(idCounter.getAndIncrement());
}

java.util.UUID: toString()

具有计数信息的唯一ID

import java.util.concurrent.atomic.AtomicLong;

public class RandomIdUtils {

    private static AtomicLong atomicCounter = new AtomicLong();

    public static String createId() {

        String currentCounter = String.valueOf(atomicCounter.getAndIncrement());
        String uniqueId = UUID.randomUUID().toString();

        return uniqueId + "-" + currentCounter;
    }
}

String name,password;

public int idGen() {

    int id = this.name.hashCode() + this.password.hashCode();
    int length = String.valueOf(id).length();
    int Max_Length = 5;
    if(String.valueOf(id).length()>Max_Length) 
    {
        id = (int) (id /Math.pow(10.0,length - Max_Length ));
    }
    return  id;
}

创建UUID。

String uniqueID = UUID.randomUUID().toString();

如果你想要简短的、人类可读的id，并且只需要它们在每次JVM运行时是唯一的:

private static long idCounter = 0;

public static synchronized String createID()
{
    return String.valueOf(idCounter++);
}    

编辑:评论中建议的替代方案-这依赖于底层的线程安全“魔法”，但更可扩展，同样安全:

private static AtomicLong idCounter = new AtomicLong();

public static String createID()
{
    return String.valueOf(idCounter.getAndIncrement());
}