打印arraylist元素？ [英] print arraylist element?

问题描述

如何在arraylistlist中打印元素e？

how do i print the element "e" in arraylist "list" out?

 ArrayList<Dog> list = new ArrayList<Dog>();
 Dog e = new Dog();
 list.add(e);
 System.out.println(list);

推荐答案

是否要打印整个列表或者你想要的迭代列表中的每个元素？无论哪种方式打印任何有意义的 Dog 类都需要覆盖 toString（）方法（如其他答案中所述）从 Object 类返回有效结果。

Do you want to print the entire list or you want to iterate through each element of the list? Either way to print anything meaningful your Dog class need to override the toString() method (as mentioned in other answers) from the Object class to return a valid result.

public class Print {
    public static void main(final String[] args) {
        List<Dog> list = new ArrayList<Dog>();
        Dog e = new Dog("Tommy");
        list.add(e);
        list.add(new Dog("tiger"));
        System.out.println(list);
        for(Dog d:list) {
            System.out.println(d);
            // prints [Tommy, tiger]
        }
    }

    private static class Dog {
        private final String name;
        public Dog(final String name) {
            this.name = name;
        }

        @Override
        public String toString() {
            return name;
        }
    }
}

此代码的输出是：

[Tommy, tiger]  
Tommy  
tiger

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