Java ArrayList.remove()

Question

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Is Java "pass-by-reference" or "pass-by-value"? (91 个回答)

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我想从 t1 中删除单词“a”目的。为什么t2对象也受到影响？

代码:

package newproject;

import java.util.ArrayList;
import java.util.Arrays;

public class NewProject {

    public static void main(String[] args) {      
        String str[] = {"a", "b", "c"};
        ArrayList<String> words = new ArrayList<>();
        words.addAll(Arrays.asList(str));

        Test t1 = new Test(words);
        Test t2 = new Test(words);

        System.out.println("Result Before ");
        System.out.println("T1 " + t1.getWords());
        System.out.println("T2 " + t2.getWords());

        // Only T1 remove words, not T2
        t1.removeWords("a");

        System.out.println("Result After ");
        System.out.println("T1 " + t1.getWords());
        System.out.println("T2 " + t2.getWords());
    }   

}

class Test {
    private ArrayList<String> words;

    Test(ArrayList<String> words){
        setWords(words);
    }

    void setWords(ArrayList<String> words){
        this.words = words;
    }

    ArrayList <String> getWords() {
        return this.words;
    }

    void removeWords(String word) {
        this.words.remove(word);
    }
}

Answer 1

因为 t1 和 t2 共享相同的 ArrayList 。而不是传递 ArrayList在构造函数中，您希望构造函数说 this.words = new ArrayList<String>();确保 Test 的每个实例有自己的 Collection 。