src/chapter4/Example25.java

@@ -1,14 +1,4 @@
 package chapter4;
 
-public class Example25 {
+public class Examaple25 {
-    public static void main(String[] args) {
-        int result = divide(4, 0);
-        System.out.println("结果：" + result);
-
-        System.out.println("程序继续运行...");
-    }
-
-    public static int divide(int x, int y) {
-        return x / y;
-    }
 }

src/chapter4/example14/Example14.java

@@ -1,36 +1,2 @@
-package chapter4.example14;
+package chapter4.example14;public class Example14 {
-
-abstract class Animal {
-    abstract void shout();
-}
-
-class Cat extends Animal {
-    public void shout() {
-        System.out.println("喵喵...");
-    }
-}
-
-class Dog extends Animal {
-    public void shout() {
-        System.out.println("汪汪...");
-    }
-}
-
-class Example14 {
-    public static void main(String[] args) {
-        Animal cat = new Cat();
-        Animal dog = new Dog();
-
-        cat.shout();
-        dog.shout();
-    }
-}
-
-class Example15 {
-    public static void main(String[] args) {
-        Dog dog = new Dog();
-        Animal an = dog;
-
-        an.shout();
-    }
 }

src/chapter4/object/Test.java

@@ -1,7 +1,5 @@
 package chapter4.object;
 
-import java.util.HashSet;
-
 class Student {
     private String name;
     private int age;
@@ -11,17 +9,11 @@ class Student {
         this.age = age;
     }
 
-//    public String toString() {
+    public String toString() {
-//        return "Student {name=" + name + ", age=" + age + "}";
+        return "Student {name=" + name + ", age=" + age + "}";
-//    }
+    }
 }
 
 public class Test {
-    public static void main(String[] args) {
-        Student s1 = new Student("张三", 23);
 
-        System.out.println(s1);
-
-
-    }
 }

src/chapter5/Example01.java

@@ -1,21 +0,0 @@
-package chapter5;
-
-public class Example01 {
-    public static void main(String[] args) {
-        // 1、创建一个空的字符串
-        String str1 = new String();
-        // 2、创建一个内容为abcd的字符串
-        String str2 = new String("abcd");
-        // 3、创建一个内容为字符数组的字符串
-        char[] charArray = new char[]{'D', 'E', 'F'};
-        String str3 = new String(charArray);
-        // 4、创建一个内容为字节数组的字符串
-        byte[] arr = {97, 98, 99};
-        String str4 = new String(arr);
-
-        System.out.println("a" + str1 + "b");
-        System.out.println(str2);
-        System.out.println(str3);
-        System.out.println(str4);
-    }
-}

src/chapter5/Example02.java

@@ -1,13 +0,0 @@
-package chapter5;
-
-public class Example02 {
-    public static void main(String[] args) {
-        String s = "abcdabc";
-        System.out.println("字符串的长度为：" + s.length());
-        System.out.println("字符串中第一个字符:" + s.charAt(0));
-        System.out.println("字符c第一次出现的位置:" + s.indexOf('c'));
-        System.out.println("字符c最后一次出现的位置:" + s.lastIndexOf('c'));
-        System.out.println("子字符串ab第一次出现的位置：" + s.indexOf("ab"));
-        System.out.println("子字符串ab字符串最后一次出现的位置：" + s.lastIndexOf("ab"));
-    }
-}

src/chapter5/Example03.java

@@ -1,24 +0,0 @@
-package chapter5;
-
-public class Example03 {
-    public static void main(String[] args) {
-        String str = "abcdEFG";
-
-        // 1、转换成字符数组
-        System.out.print("将字符串转为字符数组后的结果:");
-        char[] charArray = str.toCharArray();
-        for (char c : charArray) {
-            System.out.print(c);    // 打印当前遍历到的字符
-            System.out.print(',');  // 每打印一个字符后，加一个逗号
-        }
-
-        // 2、把数字转换成字符串（好用）
-        System.out.println();
-        System.out.print("把数字123转换成字符串的效果：");
-        System.out.println(String.valueOf(123));
-
-        // 3、大小写转换（常用）
-        System.out.println("转换成小写：" + str.toLowerCase());
-        System.out.println("转换成大写：" + str.toUpperCase());
-    }
-}

src/chapter5/Example04.java

@@ -1,16 +0,0 @@
-package chapter5;
-
-public class Example04 {
-    public static void main(String[] args) {
-        String name = "王小明";
-        String newName = name.replace("王", "卢");
-        System.out.println("旧名字：" + name + "\n新名字：" + newName);
-
-        System.out.println();
-
-        String name2 = "   王    小明   ";
-        String name3 = name2.trim();
-        System.out.println("去除空格前：" + name2 + "\n去除空格后：" + name3 );
-        // 思考：如何去掉所有空格？
-    }
-}

src/chapter5/Example05.java

@@ -1,14 +0,0 @@
-package chapter5;
-
-public class Example05 {
-    public static void main(String[] args) {
-        String s1 = "我是王小明";
-        String s2 = "我是";
-
-        System.out.println("判断开头：" + s1.startsWith("我是"));
-        System.out.println("判断结尾：" + s1.endsWith("小明"));
-        System.out.println("判断包含：" + s1.contains("是"));
-        System.out.println("判空：" + s1.isEmpty());
-        System.out.println("判断相等：" + s1.equals(s2));
-    }
-}

src/chapter5/Example06.java

@@ -1,16 +0,0 @@
-package chapter5;
-
-public class Example06 {
-    public static void main(String[] args) {
-        String str = "石家庄-武汉-哈尔滨";
-        // 1、截取
-        System.out.println("从第5个字符截取到末尾：" + str.substring(4));
-        System.out.println("从第5个字符截取到第6个字符：" + str.substring(4, 6));
-        // 2、分割
-        System.out.println("分割后字符串数组中的元素依次是：");
-        String[] array = str.split("-");
-        for (String s : array) {
-            System.out.println(s);
-        }
-    }
-}