[英]How to Use BigDecimal add method to get sum of jtable cell values?
我在 JTable 中有一些數據。 我試圖獲得與第一列單元格值相等的第三列單元格值的總和。 以 T10 為例。 我只能得到第三列的現有值而不是總和。 我在 SO 中遵循了幾個答案,例如,
非常感謝幫助解決這個問題。
public class App_UI extends javax.swing.JFrame {
public App_UI() {
initComponents();
}
private void initComponents() {
java.awt.GridBagConstraints gridBagConstraints;
jScrollPane1 = new javax.swing.JScrollPane();
jTable1 = new javax.swing.JTable();
jButton1 = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
getContentPane().setLayout(new java.awt.GridBagLayout());
jTable1.setModel(new javax.swing.table.DefaultTableModel(
new Object [][] {
{"01", "T10", "3000", "0.25"},
{"02", "T12", "6000", "0.75"},
{"03", "T10", "4500", "0.50"},
{"04", "T16", "1500", "0.30"},
{"05", "T12", "7500", "0.85"},
{"06", "T10", "1500", "0.13"}
},
new String [] {
"Bar Mark", "Type & Size", "Length", "Weight"
}
));
jScrollPane1.setViewportView(jTable1);
gridBagConstraints = new java.awt.GridBagConstraints();
gridBagConstraints.fill = java.awt.GridBagConstraints.BOTH;
gridBagConstraints.weightx = 0.1;
gridBagConstraints.weighty = 0.1;
gridBagConstraints.insets = new java.awt.Insets(5, 5, 5, 5);
getContentPane().add(jScrollPane1, gridBagConstraints);
jButton1.setText("Print");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
gridBagConstraints = new java.awt.GridBagConstraints();
gridBagConstraints.gridx = 0;
gridBagConstraints.gridy = 1;
gridBagConstraints.insets = new java.awt.Insets(5, 5, 5, 5);
getContentPane().add(jButton1, gridBagConstraints);
pack();
}
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
DefaultTableModel model1 = (DefaultTableModel) jTable1.getModel();
for (int i = 0; i < model1.getRowCount(); i++) {
String mark = (String) model1.getValueAt(i, 1);
if (mark.equals("T10")) {
BigDecimal weights = new BigDecimal((String) model1.getValueAt(i, 3));
List<BigDecimal> listWeight = Arrays.asList(weights);
BigDecimal tWeight = listWeight.stream().reduce(BigDecimal.ZERO, BigDecimal::add);
System.out.println(tWeight);
}
}
}
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new App_UI().setVisible(true);
}
});
}
private javax.swing.JButton jButton1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTable jTable1;
}
首先,您在 if 塊中聲明了變量tWeights
,也就是說它的生命周期僅限於該塊,當標記等於“T10”時,您將在每次迭代中獲得一個新的tWeights
。
其次,您以錯誤的方式使用流,在這種情況下,使用流沒有任何優勢。 只是反復總結:
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
DefaultTableModel model1 = (DefaultTableModel) jTable1.getModel();
BigDecimal tWeight = BigDecimal.ZERO; // let's start with 0 total weight
for (int i = 0; i < model1.getRowCount(); i++) {
String mark = (String) model1.getValueAt(i, 1);
if (mark.equals("T10")) {
BigDecimal weights = new BigDecimal((String) model1.getValueAt(i, 3));
tWeight = tWeight.add(weights); // add weight to tWeight and assign the result to tWeight
System.out.println(tWeight);
}
}
}
只是另一種看法。 維護listWeight
為好:
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
DefaultTableModel model1 = (DefaultTableModel) jTable1.getModel();
BigDecimal weights;
BigDecimal tWeight = new BigDecimal("0.0");
List<BigDecimal> listWeight = new ArrayList<>();
for (int i = 0; i < model1.getRowCount(); i++) {
String mark = model1.getValueAt(i, 1).toString();
if (mark.equals("T10")) {
weights = new BigDecimal(model1.getValueAt(i, 3).toString());
listWeight.add(weights);
tWeight = tWeight.add(weights);
// System.out.println("Growing Sum -> " + tWeight);
}
}
// Display in Console Window...
System.out.println("Total sum of weights based on Size 'T10':");
StringBuilder formula = new StringBuilder("");
for (BigDecimal bdec : listWeight) {
if (!formula.toString().isEmpty()) {
formula.append(" + ");
}
formula.append(bdec);
}
formula.append(" = ").append(tWeight);
System.out.println(formula.toString());
}
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