小编Nar*_*ian的帖子

        JOptionPane.showMessageDialog(null, "a String");

我只是想知道 JOptionPane 行中的第一个参数 (null) 是什么意思以及它的用途是什么？

package javaapplication1;

public class PassString {

  public static void main(String[] args) {

      String name = "Shakespeare";

      System.out.println("In main, the name is "
              + name);

      changeName(name); // i don't get why we pass name as an argument

      System.out.println("Back in main, the name is "
              + name);
  }

  public static void changeName(String str) {
      str = "Dickens";

      System.out.println("In changeName, the name " + "is now "
              + str);
  }
}

我不理解在nameName方法中将name作为参数传递的目的.它与String name ="Shakespeare"有什么关系;

package Game;

import java.util.Scanner;

public class practice {

    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        String jack = "good, how are you?";
        System.out.println("Hello, my name is Julie the Robot");

        try{
            Thread.sleep(1000);
        }catch(InterruptedException ex) {
            Thread.currentThread().interrupt();
        }
        System.out.println("How Are You?");

        if (jack.equals(sc.nextLine())); {
        System.out.println("Im Doing Great!");
        }
        // this code is giving me an error
        else if (!jack.equals(sc.nextLine()));{


            System.out.println("Oh! So you dont care about me eh?");
        }

        try{
            Thread.sleep(700);
        }catch(InterruptedException ex) {
            Thread.currentThread().interrupt();
        }
            System.out.print("...");
        try{
                Thread.sleep(200); …