Question

我有一个类，其中的一个成员是using System; using System.Collections.Generic; using System.Windows.Forms; namespace UserObjectsLeak { public partial class FrmUserObjectsLeak : Form { // This is used to keep references of the labels being added dynamically. static readonly List<Label> Labels = new List<Label>(); public FrmUserObjectsLeak() { InitializeComponent(); } private void btnStart_Click(object sender, EventArgs e) { for (var i = 0; i < 11000; i++) { var label = new Label() { Text = i.ToString(), Width = 50 }; Labels.Add(label); try { panel1.Controls.Add(label); } catch (System.ComponentModel.Win32Exception ex) { lblException.Text = ex.ToString(); return; } lblControlsCount.Text = (i).ToString(); // Quick and dirty just to show the progress... Application.DoEvents(); if (i % 500 == 0) { // Remove all labels from the panel, // keep only the reference in the list. panel1.Controls.Clear(); } } } private void btnClear_Click(object sender, EventArgs e) { panel1.Controls.Clear(); Labels.Clear(); lblControlsCount.Text = ""; lblException.Text = ""; } #region Designer code /// <summary> /// Required designer variable. /// </summary> private System.ComponentModel.IContainer components = null; /// <summary> /// Clean up any resources being used. /// </summary> /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param> protected override void Dispose(bool disposing) { if (disposing && (components != null)) { components.Dispose(); } base.Dispose(disposing); } #region Windows Form Designer generated code /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> private void InitializeComponent() { this.label1 = new System.Windows.Forms.Label(); this.label2 = new System.Windows.Forms.Label(); this.btnStart = new System.Windows.Forms.Button(); this.lblControlsCount = new System.Windows.Forms.Label(); this.btnClear = new System.Windows.Forms.Button(); this.panel1 = new System.Windows.Forms.FlowLayoutPanel(); this.lblException = new System.Windows.Forms.Label(); this.SuspendLayout(); // // label1 // this.label1.AutoSize = true; this.label1.Location = new System.Drawing.Point(15, 17); this.label1.Name = "label1"; this.label1.Size = new System.Drawing.Size(191, 13); this.label1.TabIndex = 0; this.label1.Text = "Click the button to start adding controls"; // // label2 // this.label2.AutoSize = true; this.label2.Location = new System.Drawing.Point(12, 95); this.label2.Name = "label2"; this.label2.Size = new System.Drawing.Size(77, 13); this.label2.TabIndex = 1; this.label2.Text = "controls count:"; // // btnStart // this.btnStart.Location = new System.Drawing.Point(12, 49); this.btnStart.Name = "btnStart"; this.btnStart.Size = new System.Drawing.Size(75, 23); this.btnStart.TabIndex = 2; this.btnStart.Text = "Start"; this.btnStart.UseVisualStyleBackColor = true; this.btnStart.Click += new System.EventHandler(this.btnStart_Click); // // lblControlsCount // this.lblControlsCount.AutoSize = true; this.lblControlsCount.Location = new System.Drawing.Point(95, 95); this.lblControlsCount.Name = "lblControlsCount"; this.lblControlsCount.Size = new System.Drawing.Size(0, 13); this.lblControlsCount.TabIndex = 3; // // btnClear // this.btnClear.Location = new System.Drawing.Point(98, 49); this.btnClear.Name = "btnClear"; this.btnClear.Size = new System.Drawing.Size(75, 23); this.btnClear.TabIndex = 5; this.btnClear.Text = "Clear"; this.btnClear.UseVisualStyleBackColor = true; this.btnClear.Click += new System.EventHandler(this.btnClear_Click); // // panel1 // this.panel1.FlowDirection = System.Windows.Forms.FlowDirection.TopDown; this.panel1.Location = new System.Drawing.Point(226, 17); this.panel1.Name = "panel1"; this.panel1.Size = new System.Drawing.Size(200, 148); this.panel1.TabIndex = 6; // // lblException // this.lblException.AutoSize = true; this.lblException.Location = new System.Drawing.Point(15, 179); this.lblException.Name = "lblException"; this.lblException.Size = new System.Drawing.Size(0, 13); this.lblException.TabIndex = 7; // // frmUserObjectsLeak // this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F); this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font; this.ClientSize = new System.Drawing.Size(452, 308); this.Controls.Add(this.lblException); this.Controls.Add(this.panel1); this.Controls.Add(this.btnClear); this.Controls.Add(this.lblControlsCount); this.Controls.Add(this.btnStart); this.Controls.Add(this.label2); this.Controls.Add(this.label1); this.Name = "FrmUserObjectsLeak"; this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen; this.Text = "User Objects Leak Demo"; this.ResumeLayout(false); this.PerformLayout(); } #endregion private System.Windows.Forms.Label label1; private System.Windows.Forms.Label label2; private System.Windows.Forms.Button btnStart; private System.Windows.Forms.Label lblControlsCount; private System.Windows.Forms.Button btnClear; private System.Windows.Forms.FlowLayoutPanel panel1; private System.Windows.Forms.Label lblException; #endregion Designer code } }，所以我有一个采用相同类型的构造函数，一切都很好。

ArrayList<ArrayList<Double>> elements

但是，我还需要能够使用类型为public elementArray(ArrayList<ArrayList<Double>> elements) { this.elements = elements; // a bunch of other stuff happens }的输入进行构造，因此我首先将其转换为2D列表类型，然后调用原始构造函数...

Double[][]

除了在我的构造函数中发生的第一件事外，我无法调用其他构造函数！我是否注定要在此处复制粘贴，或者有什么聪明的方法可以做我想要的事情？

Answer 1

一种解决方案是将转换提取为静态方法：

public elementArray(Double[][] array) {
    this(convert(elements));
}

private static ArrayList<ArrayList<Double>> convert(Double[][] array) {
    // convert Double[][] array to ArrayList<ArrayList<Double>> elements
}

Answer 2

调用this()之前没有代码，也不能调用其他实例方法。

您可以将该转换提取为单独的静态方法：

private static ArrayList<ArrayList<Double>> arrayToList(Double[][] d) {
    //convert and return list
}

并在第二个构造函数中重用此方法：

public elementArray(Double[][] array) {
    this(arrayToList(array));
}

Answer 3

常用的模式是改为使用Builder。

https://iluwatar.github.io/java-design-patterns/patterns/builder/

或静态工厂方法。

https://iluwatar.github.io/java-design-patterns/patterns/factory-method/

例如使用静态工厂方法，您将只有一个（可能是私有的）构造函数，该构造函数接受类所需的最原始版本。

public class elementArray{
    public elementArray(ArrayList<ArrayList<Double>> elements)
    {
        this.elements =  elements;
        // a bunch of other stuff happens
    }
    public static elementArray create(Double[][] array)
    {
        // convert Double[][] array to ArrayList<ArrayList<Double>> elements
        return new elementArray(elements);
    }
    public static elementArray create(ArrayList<ArrayList<Double>> elements)
    {
        return new elementArray(elements);
    }
}

然后，您将调用静态方法，而不是调用构造函数。

elementArray.create(new double[][]{{1.0d},{2.0d}});

在最近的Java中，Guava和Java标准库中已经相当普遍地使用了它。

请参见Arrays.asList https://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#asList-T...-

Answer 4

但是最好使用List而不是ArrayList。

    public elementArray(Double[][] array) {
        this(convert(elements));
    }

    static ArrayList<ArrayList<Double>> convert(Double[][] elements) {
        return IntStream.range(0, elements.length)
                .mapToObj(i -> IntStream.range(0, elements[i].length)
                        .mapToObj(j -> elements[i][j])
                        .collect(ArrayList::new, List::add, (u, v) -> u.addAll(v)))
                .collect(ArrayList::new,
                        (u, v) -> v.add(u),
                        (u, v) -> u.addAll(v));
    }

Java：多个构造函数强制代码重用？

4 个答案: