排序ArrayList中不显示？ [英] Sorted ArrayList not displaying?

问题描述

ArrayList <String> cdcollection = new ArrayList();

private void initButtonActionPerformed(java.awt.event.ActionEvent evt) {
    Collections.addAll(cdcollection, "renier\n",  "mert\n", "rain\n", "mylen", "dreb\n"    );
    initButton.setEnabled(false);
}

private void displayButtonActionPerformed(java.awt.event.ActionEvent evt) {

    String title1 = "Original Order\n\n";
    String title2 = "Sorted Order\n\n";

    String collection = "";
    for (int i = 0; i < cdcollection.size(); i++)  {
        collection = collection + cdcollection.get(i);
    }
    mainTextArea.setText(title1 + collection);

    Collections.sort(cdcollection);

    for (int j = 0; j < cdcollection.size(); j++)  {
        mainTextArea.setText(title2 + collection.get(j));
    }
}

private void addButtonActionPerformed(java.awt.event.ActionEvent evt) {
    cdcollection.add(cdtitleInput.getText());
}

private void removeButtonActionPerformed(java.awt.event.ActionEvent evt) {
    cdcollection.remove(cdcollection.size()-1);
}

有关此行mainTextArea.setText（TITLE2 + collection.get（J））;我得到一个错误无法找到符号，当我运行程序不显示。我看到的是这样的：

For this line mainTextArea.setText(title2 + collection.get(j)); I get an error "cannot find symbol" and it doesn't display when I run the program. All I see is this:

原始订单

renier

MERT

雨

mylen

DREB

renier
mert
rain
mylen
dreb

推荐答案

您已经定义了集像字符串字符串集合=; 。有 GET（J）中的String类被称为没有一种方法。尝试使用ArrayList对象 cdcollection 。还拿创作的ArrayList的。你已经做过类似的ArrayList＆LT;串GT; cdcollection =新的ArrayList（）; ，尽量使用泛型的两侧如的ArrayList＆LT;串GT; cdcollection =新的ArrayList＆LT;串GT;（）; ，否则你可能会得到不必要的警告

You have defined collection as a string like String collection = "";. There is no method called get(j) in String class. Try to use your arraylist object cdcollection. Also take of the creation of arraylist. You have done like ArrayList <String> cdcollection = new ArrayList();, try to use generics both the sides like ArrayList <String> cdcollection = new ArrayList<String>();, otherwise you might get unnecessary warnings.

编辑：

public static void main(String[] args){
    ArrayList<String> cdcollection = new ArrayList();
    Collections.addAll(cdcollection, "renier\n", "mert\n", "rain\n",
            "mylen", "dreb\n");

    String title1 = "Original Order\n\n";
    String title2 = "Sorted Order\n\n";

    String collection = "";
    for (int i = 0; i < cdcollection.size(); i++) {
        collection = collection + cdcollection.get(i);
    }
    System.out.println(title1 + collection);

    Collections.sort(cdcollection);
    System.out.println(cdcollection);
}

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