添加到ArrayList

Question

我不明白为什么我不能将项目添加到ArrayList。我尝试了几种不同的添加项目的方式，但它们不起作用。

class Problem { 
public ArrayList<String> problems = new ArrayList<String>(); 
public ArrayList<String> answers = new ArrayList<String>(); 

private String question1 = "What is 2+2?"; 
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); 

} 

我也曾尝试

problems.add(question1); 
problems.add(question2); 
problems.add(question3); 
problems.add(question4); 

这也不起作用。

编译器说预计标识符。

Answer 1

尝试将import java.util.ArrayList;添加到文件顶部。

你还需要一个main方法来运行，像这样的签名：如果你不改变它们计划

此外，你应该做的字符串常量final（和/或static） 。

最后，temp1是默认（“朋友”）可见性。

我假设这是一个代码片段，而不是实际运行的内容。

Answer 2

其实，你缺少一个方法声明。

尝试把代码中的Main方法里面：

public static void main(String[] args) { 
    String[] temp1 = {question1, question2, question3, question4}; 


    for (String s : temp1) 
     problems.add(s); 

    } 
} 

Answer 3

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); 
} 

}