Java 添加到ArrayList
我不明白为什么不能将项添加到ArrayList。我尝试了几种不同的添加项目的方法,但都不起作用Java 添加到ArrayList,java,arraylist,Java,Arraylist,我不明白为什么不能将项添加到ArrayList。我尝试了几种不同的添加项目的方法,但都不起作用 class Problem { public ArrayList<String> problems = new ArrayList<String>(); public ArrayList<String> answers = new ArrayList<String>(); private String question1 = "What is 2+2?
class Problem {
public ArrayList<String> problems = new ArrayList<String>();
public ArrayList<String> answers = new ArrayList<String>();
private String question1 = "What is 2+2?";
private String question2 = "What is the square root of 25";
private String question3 = "What is the next number in the sequence? {2, 4, 6}";
private String question4 = "What is 8*8?";
String[] temp1 = {question1, question2, question3, question4};
for (String s : temp1)
problems.add(s);
}
这也行不通
编译器表示需要该标识符。尝试添加import java.util.ArrayList;到您的文件的顶部
您还需要一个main方法来运行,其签名如下:
public static void main(String[] args)
此外,如果不打算更改字符串常量,则应将其设置为final和/或static
最后,temp1是默认的好友可见性
我假设这是一个代码片段,而不是您实际运行的代码。实际上,您缺少一个方法声明 尝试将代码放入主方法中:
public static void main(String[] args) {
String[] temp1 = {question1, question2, question3, question4};
for (String s : temp1)
problems.add(s);
}
}
}添加项目需要在方法或初始值设定项中。为什么要将它们放在一个数组中,然后添加到列表中?为什么不直接把它们添加到列表中呢?是的,这只是一个更大程序的一小部分。添加main方法似乎解决了我的问题。非常感谢。愚蠢的错误:P
public static void main(String[] args) {
String[] temp1 = {question1, question2, question3, question4};
for (String s : temp1)
problems.add(s);
}
}
import java.util.ArrayList;
class Problem {
public static ArrayList<String> problems = new ArrayList<String>();
public static ArrayList<String> answers = new ArrayList<String>();
private static String question1 = "What is 2+2?";
private static String question2 = "What is the square root of 25";
private static String question3 = "What is the next number in the sequence? {2, 4, 6}";
private static String question4 = "What is 8*8?";
public static void main(String [] args) {
String[] temp1 = {question1, question2, question3, question4};
for (String s : temp1)
problems.add(s);
System.out.println(""+problems);
}