[英]How to override toString method in a class
我正在尝试生成一个 jList 类。
如果我做:
package test;
import javax.swing.DefaultListModel;
public class TestFrame extends javax.swing.JFrame {
DefaultListModel jList1Model = new DefaultListModel();
public TestFrame() {
initComponents();
jList1Model.addElement(TestClass.class);
jList1.setModel(jList1Model);
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jScrollPane1 = new javax.swing.JScrollPane();
jList1 = new javax.swing.JList<>();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jList1.setModel(new javax.swing.AbstractListModel<String>() {
String[] strings = { "Item 1", "Item 2", "Item 3", "Item 4", "Item 5" };
public int getSize() { return strings.length; }
public String getElementAt(int i) { return strings[i]; }
});
jScrollPane1.setViewportView(jList1);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 380, Short.MAX_VALUE)
.addContainerGap())
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 278, Short.MAX_VALUE)
.addContainerGap())
);
pack();
}// </editor-fold>
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(TestFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(TestFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(TestFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(TestFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new TestFrame().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JList<String> jList1;
private javax.swing.JScrollPane jScrollPane1;
// End of variables declaration
}
作为我的TestClass
:
package test;
public class TestClass {
public static String name = "Test Class 1";
public int foo;
public int bar;
}
然后我得到:
到现在为止还挺好。
现在我想在 jList1 中显示name
class 属性的内容而不是class test.TestClass
test.TestClass 。
我试过这个:
public class TestClass {
public static String name = "Test Class 1";
public int foo;
public int bar;
public static String toString() {
return name;
}
}
但我什至无法编译它:
toString() in TestClass cannot override toString() in Object overriding mehtod is static.
不是覆盖toString
方法的答案,而是如何让列表显示与toString
返回的内容不同的解决方案。 将ListCellRenderer
添加到列表中。 基本上扩展默认的( JLabel
本身的扩展)并更改应显示的内容:
class ClassRenderer extends DefaultListCellRenderer {
@Override
public Component getListCellRendererComponent(
JList<?> list, Object value, int index, boolean selected, boolean focus) {
if (value instanceof Class) {
value = ((Class<?>) value).getSimpleName();
}
return super.getListCellRendererComponent(list, value, index, selected, focus);
}
}
要使用它,只需调用(在显示列表之前)
list.setCellrenderer(new ClassRenderer());
更多细节,更好的解释可以在官方教程中找到: 提供自定义渲染器
JB Nizet建议的解决方案(我的解释,希望我理解正确):创建一个对象来保存Class
及其标签; 将其实例添加到列表中:
public class LabeledClass {
private final String label;
private final Class<?> theClass;
LabeledClass(String label, Class<?> theClass) {
this.label = Objects.requireNonNull(label);
this.theClass = theClass; // TODO null check?
}
public Class<?> getTheClass() {
return theClass;
}
@Override
public String toString() {
return label;
}
// TOD hashcode, equals ?
}
用作:
model.addElement(new LabeledClass("Test", TestClass.class));
无需为此更改默认单元格渲染器。 优点:如果更改为在您的图表中使用,则更面向对象,非常简单的示例,而不是LabeledClass
:
public abstract class ChartEnricher {
private final String name;
protected ChartEnricher(String name) {
this.name = Objects.requireNonNull(name);
}
public abstract void enrichChart();
@Override
public String toString() {
return name;
}
}
必须为每个可能的条目实现enrichChart
方法,或者有一个通用的方法,该方法使用为其构造函数提供的Class
(作为LabeledClass
)。 显然,如果需要更多功能,这可以根据用例进行扩展。
以防万一它对某人有帮助,使用原始 OP 的输入,我最终将接受的答案与名为getClassName
的静态方法结合起来,该方法通过反射调用。
注意:我已经包含了使用稍微不同的名称但仍然显示反射用法的最终代码。 我的真实应用程序显然比包含的简化 OP 发布示例更复杂,因为它打算使用从抽象类扩展的许多类,这些类强制扩展类来实现多种方法。
附带说明:我唯一没有设法强制执行的是静态getClassName
方法的实现,因为显然您不能在 Java 中强制执行静态方法实现(显然抽象静态方法是不可能的)。
class IndicatorsRenderer extends DefaultListCellRenderer {
@Override
public Component getListCellRendererComponent(JList<?> list,
Object value,
int index,
boolean isSelected,
boolean cellHasFocus) {
Class<? extends BaseIndicator> baseIndicatorClass = ((Class<? extends BaseIndicator>) value);
try {
return super.getListCellRendererComponent(list, baseIndicatorClass.getMethod("getClassName").invoke(baseIndicatorClass), index, isSelected, cellHasFocus);
} catch (NoSuchMethodException ex) {
Logger.getLogger(IndicatorsRenderer.class.getName()).log(Level.SEVERE, "No such method exception while trying to access Name of indicator. Exception {0}", ex);
System.exit(1);
} catch (SecurityException ex) {
Logger.getLogger(IndicatorsRenderer.class.getName()).log(Level.SEVERE, "Security exception while trying to access Name of indicador. Exception {0}", ex);
System.exit(1);
} catch (IllegalAccessException ex) {
Logger.getLogger(IndicatorsRenderer.class.getName()).log(Level.SEVERE, "Illegal Access Exception while trying to access Name of indicator. Exception {0}", ex);
System.exit(1);
} catch (IllegalArgumentException ex) {
Logger.getLogger(IndicatorsRenderer.class.getName()).log(Level.SEVERE, "Illegal Argument Exception while trying to access Name of indicator. Exception {0}", ex);
System.exit(1);
} catch (InvocationTargetException ex) {
Logger.getLogger(IndicatorsRenderer.class.getName()).log(Level.SEVERE, "Invocation Target Exception while trying to access Name of indicator. Exception {0}", ex);
System.exit(1);
}
return null;
}
}
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