增、删、查都完成了！

src/com/msksbr/MainFrm/MenuBar.java

@@ -1,12 +1,9 @@
 package com.msksbr.MainFrm;
 
+import com.msksbr.MainFrm.MenuItemDiaog.*;
 import com.msksbr.MainFrm.MenuItemDiaog.Adder.BookAdder;
 import com.msksbr.MainFrm.MenuItemDiaog.Adder.RentAdder;
 import com.msksbr.MainFrm.MenuItemDiaog.Adder.StudentAdder;
-import com.msksbr.MainFrm.MenuItemDiaog.AuthorDIalog;
-import com.msksbr.MainFrm.MenuItemDiaog.MITDialog;
-import com.msksbr.MainFrm.MenuItemDiaog.SearchDIalog;
-import com.msksbr.MainFrm.MenuItemDiaog.aboutDIalog;
 
 import javax.swing.*;
 import java.awt.event.ActionEvent;
@@ -76,8 +73,23 @@ public class MenuBar extends JMenuBar {
         // ”删除“菜单
         JMenu removeMenu = new JMenu("删除");
         JMenuItem bookRemove = new JMenuItem("删除图书信息");
+        bookRemove.addActionListener(new ActionListener() {
+            public void actionPerformed(ActionEvent e) {
+                new Remover("books");
+            }
+        });
         JMenuItem studentRemove = new JMenuItem("删除学生信息");
+        studentRemove.addActionListener(new ActionListener() {
+            public void actionPerformed(ActionEvent e) {
+                new Remover("students");
+            }
+        });
         JMenuItem rentRemove = new JMenuItem("删除借阅信息");
+        rentRemove.addActionListener(new ActionListener() {
+            public void actionPerformed(ActionEvent e) {
+                new Remover("rents");
+            }
+        });
         removeMenu.add(bookRemove);
         removeMenu.add(studentRemove);
         removeMenu.add(rentRemove);

src/com/msksbr/MainFrm/MenuItemDiaog/Remover.form

@@ -0,0 +1,66 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<form xmlns="http://www.intellij.com/uidesigner/form/" version="1" bind-to-class="com.msksbr.MainFrm.MenuItemDiaog.Remover">
+  <grid id="cbd77" binding="contentPane" layout-manager="GridLayoutManager" row-count="2" column-count="1" same-size-horizontally="false" same-size-vertically="false" hgap="-1" vgap="-1">
+    <margin top="10" left="10" bottom="10" right="10"/>
+    <constraints>
+      <xy x="48" y="54" width="436" height="297"/>
+    </constraints>
+    <properties/>
+    <border type="none"/>
+    <children>
+      <grid id="94766" layout-manager="GridLayoutManager" row-count="1" column-count="1" same-size-horizontally="false" same-size-vertically="false" hgap="-1" vgap="-1">
+        <margin top="0" left="0" bottom="0" right="0"/>
+        <constraints>
+          <grid row="1" column="0" row-span="1" col-span="1" vsize-policy="1" hsize-policy="3" anchor="0" fill="3" indent="0" use-parent-layout="false"/>
+        </constraints>
+        <properties/>
+        <border type="none"/>
+        <children>
+          <grid id="9538f" layout-manager="FlowLayout" hgap="5" vgap="5" flow-align="1">
+            <constraints>
+              <grid row="0" column="0" row-span="1" col-span="1" vsize-policy="3" hsize-policy="3" anchor="0" fill="3" indent="0" use-parent-layout="false"/>
+            </constraints>
+            <properties/>
+            <border type="none"/>
+            <children>
+              <component id="e7465" class="javax.swing.JButton" binding="buttonOK">
+                <constraints/>
+                <properties>
+                  <text value="删除"/>
+                </properties>
+              </component>
+            </children>
+          </grid>
+        </children>
+      </grid>
+      <grid id="e3588" layout-manager="BorderLayout" hgap="0" vgap="0">
+        <constraints>
+          <grid row="0" column="0" row-span="1" col-span="1" vsize-policy="3" hsize-policy="3" anchor="0" fill="3" indent="0" use-parent-layout="false"/>
+        </constraints>
+        <properties/>
+        <border type="none"/>
+        <children>
+          <component id="1b7c" class="javax.swing.JLabel" binding="idLable">
+            <constraints border-constraint="West"/>
+            <properties>
+              <text value=""/>
+            </properties>
+          </component>
+          <grid id="8147a" layout-manager="FlowLayout" hgap="5" vgap="5" flow-align="0">
+            <constraints border-constraint="Center"/>
+            <properties/>
+            <border type="none"/>
+            <children>
+              <component id="19c5" class="javax.swing.JTextField" binding="idField">
+                <constraints/>
+                <properties>
+                  <columns value="15"/>
+                </properties>
+              </component>
+            </children>
+          </grid>
+        </children>
+      </grid>
+    </children>
+  </grid>
+</form>

src/com/msksbr/MainFrm/MenuItemDiaog/Remover.java

@@ -0,0 +1,106 @@
+package com.msksbr.MainFrm.MenuItemDiaog;
+
+import com.msksbr.LoginFrm.ScreenSize;
+import com.msksbr.SQL.Connector;
+
+import javax.swing.*;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+public class Remover extends JDialog {
+    private JPanel contentPane;
+    private JButton buttonOK;
+    private JLabel idLable;
+    private JTextField idField;
+    private String table;
+    private String Searchsql;
+    private String searchSQL;
+    private String deleteSQL;
+    private String searchErrMsg;
+    private int id;
+    private Connector searchConnector;
+    private Connector deleteConnector;
+
+    public Remover(String table) {
+        try {
+            searchConnector = new Connector();
+            deleteConnector = new Connector();
+        } catch (ClassNotFoundException e) {
+            throw new RuntimeException(e);
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+        buttonOK.addActionListener(new ActionListener() {
+            public void actionPerformed(ActionEvent e) {
+                onOK();
+            }
+        });
+        this.table = table;
+        if (table.equals("books")) {
+            setTitle("删除图书信息");
+            idLable.setText("请输入书号：");
+            searchErrMsg = "未找到该图书信息";
+        } else if (table.equals("students")) {
+            setTitle("删除学生信息");
+            idLable.setText("请输入学号：");
+            searchErrMsg = "未找到该学生信息";
+        } else if (table.equals("rents")) {
+            setTitle("删除借阅信息");
+            idLable.setText("请输入书号：");
+            searchErrMsg = "未找到该借阅信息";
+        }
+        setContentPane(contentPane);
+        setModal(true);
+        getRootPane().setDefaultButton(buttonOK);
+        pack();
+        setResizable(false);
+        setLocation();
+        setVisible(true);
+    }
+
+    private void onOK() {
+        // 在此处添加您的代码
+        try {
+            this.id = Integer.valueOf(idField.getText());
+            searchSQLMaker();
+            deleteSQLMaker();
+            ResultSet rs = searchConnector.executeQuery(searchSQL);
+            if (rs.next()) {
+                deleteConnector.executeUpdate(deleteSQL);
+            } else {
+                JOptionPane.showMessageDialog(this, searchErrMsg, "错误", JOptionPane.WARNING_MESSAGE);
+            }
+        } catch (NumberFormatException e) {
+            JOptionPane.showMessageDialog(this, "请输入一个整数", "错误", JOptionPane.ERROR_MESSAGE);
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+        dispose();
+    }
+
+    private void searchSQLMaker() {
+        if (table.equals("books")) {
+            searchSQL = "select * from " + table + " where book_id=" + id + ";";
+        } else if (table.equals("students")) {
+            searchSQL = "select * from " + table + " where student_id=" + id + ";";
+        } else if (table.equals("rents")) {
+            searchSQL = "select * from " + table + " where book_id=" + id + ";";
+        }
+    }
+
+    private void deleteSQLMaker() {
+        if (table.equals("books")) {
+            deleteSQL = "delete from " + table + " where book_id=" + id + ";";
+        } else if (table.equals("students")) {
+            deleteSQL = "delete from " + table + " where student_id=" + id + ";";
+        } else if (table.equals("rents")) {
+            deleteSQL = "UPDATE books SET borrowed_by = null WHERE book_id=" + id + ";";
+        }
+    }
+
+    public void setLocation() {
+        setLocation(new ScreenSize().width / 2 - getWidth() / 2, new ScreenSize().height / 2 - getHeight() / 2);
+    }
+}