仅在移动表格或单击表格后才显示该值的原因是，这样做会强制重新绘制.
您可以通过在done[5] = 10;

The reason why the value shows only after you move the table or click on it, is that by doing so you force a repaint.
You can verify it by invoking frame.repaint() after done[5] = 10;

以下是一个文件的MRE(将整个代码复制粘贴到FinalClass.java中并运行):

The following is a one-file MRE (copy paste the entire code into FinalClass.java and run):

import java.awt.Color;
import java.awt.Component;
import java.util.Arrays;    
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTable;
import javax.swing.SwingConstants;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableCellRenderer;

public class FinalClass {

    private final JFrame frame = new JFrame();
    private final int[] done = new int[90]; //better avoid static
    private final Integer[][] slip = new Integer[9][5];
    private final String colHeader[] = {"1","2","3","4","5"};
    private JTable table;

    FinalClass() {

        Arrays.fill(done, -1);
        int cnt = 0;
        for(int x = 0; x<9; x++ ) {
            for(int y = 0; y <5; y++) {
                slip[x][y] = cnt++;
            }
        }

        DefaultTableModel tableModel = new DefaultTableModel(slip, colHeader) {
            private static final long serialVersionUID = 1L;
            @Override
            public boolean isCellEditable(int row, int column) {
               //all cells false
               return false;
            }
        };

        table = new JTable(slip, colHeader);
        table.setDefaultRenderer(Object.class, new MyRenderer());
        table.setModel(tableModel);
        frame.add(table);
        frame.pack();
        frame.setVisible(true);
    }

    private void refresh(){
        frame.repaint();
    }

    void done(int index, int value){
        done[index] = value;
        refresh();
    }

    public static void main(String[] args) {

        FinalClass f = new FinalClass();
        try {
            Thread.sleep(3000);
            f.done(5, 10);
        } catch(Exception e) { e.printStackTrace(); }
    }

    //follow java naming conventions
    class MyRenderer extends JLabel implements TableCellRenderer {

           private static final long serialVersionUID = 1L;

           public MyRenderer()
           {
               super.setOpaque(true);
           }

           @Override
           public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus,
                   int row, int column) {
               setHorizontalAlignment(SwingConstants.CENTER);
               setText(value.toString());
               Color myColor = new Color(255, 253, 117);
               setBackground(myColor);
               if((int)value == -1)
               {
                   value = null;
                   setText("");
                   return this;
               }
               for(int i = 0; i < 90; i++) {
                   if((int)value == done[i]) //this value changes during the program.
                   {
                       setBackground(Color.cyan);
                   }
               }
               return this;
           }
        }
}

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旁注:
1.如果您希望表自动响应不断变化的数据中的更改，则需要将更改应用于其模型，如此示例中所示回答您先前的问题.

---

Side notes:
1. If you want the table to respond automatically to change in the undelying data, you need to apply the change to its model as demonstrated in this answer to your previous question.

2.从多个线程修改done需要同步.
3.建议遵循 Java命名约定

2.Modifying done from more than one thread needs to be synchronized.
3.It is recommended to follow Java Naming Conventions