Comparable 重写 compareTo两个参数报错—排序

  1. public class ComparatorDemo {
  2.     public static void main(String[] args) {
  3.         ArrayList<String> arr = new ArrayList<>();
  4.         arr.add("aaa");
  5.         arr.add("bb");
  6.         arr.add("cccc");
  7.         arr.add("d");
  8.         System.out.println(arr);
  9.         //Collections.sort(arr,getComparator());
  10.         System.out.println(arr);
  12.     }
  13.     private static Comparable<String> getComparator(){
  14. //        return new Comparable<String>() {
  15. //            @Override
  16. //            public int compareTo(String s2,String s1) {
  17. //                return s2.length()-s1.length();
  18. //            }
  19. //        };
  20.         //不知道为啥报错,它不允许两个参数
  21.        return (s1,s2) -> s1.length()-s2.length();
  22.     }
  23. }

Supplier函数式接口

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  1. import java.util.function.Supplier;
  3. public class SupplierDemo {
  4.     public static void main(String[] args) {
  5.         String s = getString(() -> "柳夜熙") ;
  6.         System.out.println(s);
  7.         //>>>柳夜熙
  9.         Integer i = getInteger(()->80);
  10.         System.out.println(i);
  11.         //>>>80
  12.     }
  14.     private static String getString(Supplier<String> s) {
  15.         return s.get();
  16.     }
  17.     private static Integer getInteger(Supplier<Integer> s) {
  18.         return s.get();
  19.     }
  20. }
  1. import java.util.function.Supplier;
  3. public class SuplierTest {
  4.     public static void main(String[] args) {
  5.         int[] arr = {88, 1, 2, 3, 5, 8, 13, 21, 34};
  6.         int Max = getMax(() -> {
  7.             int max = arr[0];
  8.             for (int i : arr) {
  9.                 if (i > max) {
  10.                     max = i;
  11.                 }
  12.             }
  13.             return max;
  14.         });
  15.         System.out.println(Max);
  16.     }
  18.     private static int getMax(Supplier<Integer> sup) {
  19.         return sup.get();
  20.     }
  21. }

Consumer函数式接口

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  1. import java.util.function.Consumer;
  3. public class ConsumerDemo {
  4.     public static void main(String[] args) {
  5.         operatorString("柳夜熙", s -> System.out.println(s));
  6.         operatorString("青染", System.out::println);
  7.         operatorString("反着读", s -> System.out.println(new StringBuilder(s).reverse().toString()));
  9.         operatorString("牙刷", s -> System.out.println(s), s -> System.out.println(new StringBuilder(s).reverse().toString()));
  11.     }
  13.     private static void operatorString(String name, Consumer<String> con) {
  14.         con.accept(name);
  15.     }
  17.     private static void operatorString(String name, Consumer<String> con1, Consumer<String> con2) {
  18.         /*  方式一:
  19.         con1.accept(name);
  20.         con2.accept(name);
  21.         */
  23.         //方式二:
  24.         con1.andThen(con2).accept(name);
  25.         /*  源码 andThen
  26.             default Consumer<T> andThen(Consumer<? super T> after) {
  27.             Objects.requireNonNull(after);
  28.             return (T t) -> { accept(t); after.accept(t); };
  29.             }
  30.         */
  31.     }
  32. }
  1. import java.util.function.Consumer;
  3. public class ConsumerTest {
  4.     public static void main(String[] args) {
  5.         String[] strArr = {"张飞,35", "武则天,28", "孙悟空,500"};
  7.         printInfo(strArr, s -> {
  8.             String name = s.split(",")[0];
  9.             System.out.print(name);
  10.         }, s -> {
  11.             Integer age = Integer.parseInt(s.split(",")[1]);
  12.             System.out.println(age);
  13.         });
  14.     }
  15.     //>>>   张飞35
  16.     //      武则天28
  17.     //      孙悟空500
  18.     private static void printInfo(String[] strArr, Consumer<String> con1, Consumer<String> con2) {
  19.         for (String s : strArr) {
  20.             con1.andThen(con2).accept(s);
  21.         }
  22.     }
  23. }

Predicate函数式接口

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  1. import java.util.function.Predicate;
  3. public class PredicateDemo {
  4.     public static void main(String[] args) {
  5.         Boolean b1 = checkString("Hello", s -> s.length() > 8);
  6.         System.out.println(b1);
  7.         //>>> false
  8.         Boolean b2 = checkString("Hello", s -> s.length() < 8);
  9.         System.out.println(b2);
  10.         //>>> true
  12.         boolean b3 = checkString("world", s -> s.length() > 5, s -> s.length() < 5);
  13.         System.out.println(b3);
  14.         //>>> false
  15.     }
  17.     private static boolean checkString(String s, Predicate<String> pre1,Predicate<String> pre2) {
  18.         /*boolean b1 = pre1.test(s);
  19.         boolean b2 = pre2.test(s);
  20.         boolean b = b1 && b2;
  21.         return b;*/
  23.         //return pre1.and(pre2).test(s);  //逻辑与
  24.         return pre1.or(pre2).test(s);   //逻辑或
  25.         /**
  26.          *     default Predicate<T> or(Predicate<? super T> other) {
  27.          *         Objects.requireNonNull(other);
  28.          *         return (t) -> test(t) || other.test(t);
  29.          *     }
  30.          */
  31.     }
  34.     private static boolean checkString(String s, Predicate<String> pre) {
  36.         //return pre.test(s);
  38.         //取反
  39.         //return !pre.test(s);
  40.         return pre.negate().test(s);  //逻辑非
  41.         /*
  42.             default Predicate<T> negate() {
  43.             return (t) -> !test(t);
  44.             }
  45.          */
  46.     }
  47. }

predicate条件筛选

  1. import java.util.ArrayList;
  2. import java.util.function.Predicate;
  4. /**
  5.  * 条件筛选 --> 名字长度大于2,年龄大于30
  6.  */
  8. public class PredicateTest {
  9.     public static void main(String[] args) {
  10.         String[] strArr = {"张伟,40", "曾小贤,38", "胡一菲,28", "唐悠悠,25"};
  11.         ArrayList<String> arr = myFilter(strArr, s -> s.split(",")[0].length() > 2, s -> Integer.parseInt(s.split(",")[1]) > 30);
  12.         System.out.println(arr);
  13.         //>>> [曾小贤,38]
  14.     }
  16.     private static ArrayList<String> myFilter(String[] strArr, Predicate<String> pre1, Predicate<String> pre2) {
  17.         ArrayList<String> arr = new ArrayList<>();
  18.         for (String s : strArr) {
  19.             if (pre1.and(pre2).test(s)) {
  20.                 arr.add(s);
  21.             }
  22.         }
  23.         return arr;
  24.     }
  25. }

Function函数式接口

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  1. import java.util.function.Function;
  3. public class FunctionDemo {
  4.     public static void main(String[] args) {
  5.         convert("100", s -> Integer.parseInt(s));
  6.         convert("100", Integer::parseInt);
  8.         convert(888, i -> i.toString());
  9.         convert(888, i -> String.valueOf(i + 666));
  11.         convert("2", s -> Integer.parseInt(s) * 10, i -> i.toString());
  12.     }
  14.     //字符串转int类型
  15.     private static void convert(String s, Function<String, Integer> func) {
  16.         Integer i = func.apply(s);
  17.         System.out.println(i);
  18.         //>>> 100
  19.         //    100
  20.     }
  22.     //int转字符串
  23.     private static void convert(int i, Function<Integer, String> func) {
  24.         String s = func.apply(i);
  25.         System.out.println(s);
  26.         //>>> 888
  27.         //    1554
  28.     }
  30.     //字符串转int类型,做乘法后,再转字符串
  31.     private static void convert(String s, Function<String, Integer> func1, Function<Integer, String> func2) {
  32.         Integer i = func1.apply(s);
  33.         String ss = func2.apply(i);
  34.         System.out.println(ss);
  35.         //>>> 20
  36.         //方式二
  37.         String ss1 = func1.andThen(func2).apply(s);
  38.         System.out.println(ss1);
  39.         //>>> 20
  40.         /**
  41.          *      default <V> Function<T, V> andThen(Function<? super R, ? extends V> after) {
  42.          *         Objects.requireNonNull(after);
  43.          *         return (T t) -> after.apply(apply(t));
  44.          *      }
  45.          */
  46.     }
  47. }
  1. import java.util.function.Function;
  3. public class FunctionTest {
  4.     public static void main(String[] args) {
  5.         useFunction("租八戒,300",s -> Integer.parseInt(s.split(",")[1])+700,i -> new StringBuilder("租八戒,").append(i).toString());
  6.     }
  8.     private static void useFunction(String s, Function<String,Integer> fun1,Function<Integer,String> fun2) {
  9.         String ss = fun1.andThen(fun2).apply(s);
  10.         System.out.println(ss);
  11.         //>>> 租八戒,1000
  12.     }
  13. }

Stream流

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普通方式

  1. import java.util.ArrayList;
  3. public class StreamDemo {
  4.     public static void main(String[] args) {
  5.         String[] strArr = {"张国荣", "张伟", "李张洋", "张飞", "王红", "张三", "张惠妹"};
  6.         ArrayList<String> arrZ = new ArrayList<>();  //筛选姓张的
  7.         for (String s : strArr) {
  8. //            if (s.substring(0,1).equals("张")){
  9. //                arrZ.add(s);
  10. //            }
  11.             if (s.startsWith("张")){
  12.                 arrZ.add(s);
  13.             }
  14.         }
  15.         System.out.println(arrZ);
  16.         ArrayList<String> arrZ3 = new ArrayList<>();
  17.         for (String s: arrZ){
  18.             if (s.length()>2){
  19.                 arrZ3.add(s);
  20.             }
  21.         }
  22.         System.out.println(arrZ3);
  23.     }
  24. }

使用Stream流

  1. public class StreamTest {
  2.     public static void main(String[] args) {
  3.         ArrayList<String> strArr = new ArrayList<>();
  4.         //String[] strArr = {"张国荣", "张伟", "李张洋", "张飞", "王红", "张三", "张惠妹"};
  5.         strArr.add("张国荣");
  6.         strArr.add("张伟");
  7.         strArr.add("李张洋");
  8.         strArr.add("张飞");
  9.         strArr.add("王红");
  10.         strArr.add("张三");
  11.         strArr.add("张惠妹");
  12.         strArr.stream().filter(s -> s.startsWith("张")).filter(s -> s.length() > 2).forEach(s -> System.out.println(s));
  13.         System.out.println("----");
  14.         strArr.stream().filter(s -> s.startsWith("张")).filter(s -> s.length() > 2).forEach(System.out::println);
  15.     }
  16. }
  1. import java.util.ArrayList;
  2. import java.util.HashMap;
  3. import java.util.stream.Stream;
  5. public class StreamTest {
  6.     public static void main(String[] args) {
  7.         //Collections 体系 直接生成
  8.         ArrayList<String> strArr = new ArrayList<>();
  9.         strArr.add("张国荣");
  10.         strArr.add("张伟");
  11.         strArr.add("李张洋");
  12.         strArr.add("张飞");
  13.         strArr.add("王红");
  14.         strArr.add("张三");
  15.         strArr.add("张惠妹");
  16.         strArr.stream().filter(s -> s.startsWith("张")).filter(s -> s.length() > 2).forEach(s -> System.out.println(s));
  17.         System.out.println("----");
  18.         strArr.stream().filter(s -> s.startsWith("张")).filter(s -> s.length() > 2).forEach(System.out::println);
  19.         System.out.println("----");
  20.         //数组
  21.         String[] strArr1 = {"张国荣", "张伟", "李张洋", "张飞", "王红", "张三", "张惠妹"};
  22.         Stream.of(strArr1).filter(s -> s.startsWith("张")).filter(s -> s.length() > 2).forEach(System.out::println);
  24.         //Map体系集合 间接生成流
  25.         HashMap<Integer, String> map = new HashMap<>();
  26.         map.put(1, "张国荣");
  27.         map.put(2, "张伟");
  28.         map.put(3, "李张洋");
  29.         map.put(4, "张飞");
  30.         map.put(5, "王红");
  31.         map.put(6, "张三");
  32.         map.put(7, "张惠妹");
  33.         //map.keySet().stream().filter(i -> i>3).forEach(System.out::println);
  34.         map.values().stream().filter(s -> s.startsWith("张")).filter(s -> s.length() > 2).forEach(System.out::println);
  35.     }
  36. }

image.png

Stream 方法

  1. import java.util.ArrayList;
  2. import java.util.stream.Stream;
  4. public class StreamDemo01 {
  5.     public static void main(String[] args) {
  6.         ArrayList<String> strArr = new ArrayList<>();
  7.         strArr.add("张国荣");
  8.         strArr.add("张伟");
  9.         strArr.add("李张洋");
  10.         strArr.add("张飞");
  11.         strArr.add("王红");
  12.         strArr.add("张三");
  13.         strArr.add("张惠妹");
  14.         //取 前5个元素
  15.         Stream<String> limit = strArr.stream().limit(5);
  16.         //limit.forEach(System.out::println);
  18.         //跳过 前2个元素
  19.         Stream<String> skip = strArr.stream().skip(2);
  20.         //skip.forEach(System.out::println);
  22.         System.out.println("----");
  24.         //concat 连接两个流
  25.         //Stream.concat(limit, skip).forEach(System.out::println);
  26.         //>>> 抛出异常:stream has already been operated upon or closed
  27.         //原因 : 前方的limit和skip流 已使用了forEach关闭.
  29.         //distinct 去重
  30.         Stream.concat(limit, skip).distinct().forEach(System.out::println);
  32.         //int[] arr = {7, 5, 9, 2, 6, 3, 5, 1, 2, 8, 4}; -->
  33.         // Redundant 'sorted' call: stream contains at most one element
  34.         Integer[] arr = {7, 5, 9, 2, 6, 3, 5, 1, 8, 4};
  35.         Stream.of(arr).sorted().forEach(System.out::print);
  36.         System.out.println();
  37.         String[] sarr = {"b", "d", "c", "f", "a", "e", "g"};
  38.         Stream.of(sarr).sorted().forEach(System.out::print);
  39.         System.out.println();
  40.         Stream.of(sarr).map(s -> stringToAscii(s)).forEach(s -> System.out.print(s+"+"));
  41.         //求和
  42.         int sum = Stream.of(sarr).map(s -> stringToAscii(s)).mapToInt(Integer::parseInt).sum();
  43.         System.out.println("\n"+sum);
  44.         //统计个数
  45.         long count = Stream.of(sarr).count();
  46.         System.out.println(count);
  47.     }
  49.     /**
  50.      * 字符串转换为Ascii
  51.      *
  52.      * @param value
  53.      * @return
  54.      */
  55.     public static String stringToAscii(String value) {
  56.         StringBuffer sbu = new StringBuffer();
  57.         char[] chars = value.toCharArray();
  58.         for (int i = 0; i < chars.length; i++) {
  59.             if (i != chars.length - 1) {
  60.                 sbu.append((int) chars[i]).append(",");
  61.             } else {
  62.                 sbu.append((int) chars[i]);
  63.             }
  64.         }
  65.         return sbu.toString();
  66.     }
  67. }

Stream收集操作

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类加载

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  1. public class ClassloaderDemo {
  2.     public static void main(String[] args) {
  3.         ClassLoader c = ClassLoader.getSystemClassLoader();
  4.         System.out.println(c);
  5.         //>>> Launcher$AppClassLoader 系统类加载器
  7.         ClassLoader c1 = c.getParent(); //返回父类加载器
  8.         System.out.println(c1);
  9.         //>>> Launcher$ExtClassLoader  平台类加载器
  11.         System.out.println(c1.getParent());
  12.         //null  内置类加载器Bootstrap,通常表示为null
  14.     }
  15. }

反射

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Student

  1. public class Student {
  2.     private String name;
  3.     int age;
  4.     public String address;
  6.     public Student() {
  8.     }
  10.     private Student(String name, String address) {
  11.         this.name = name;
  12.         this.address = address;
  13.     }
  15.     public Student(String name, int age, String address) {
  16.         this.name = name;
  17.         this.age = age;
  18.         this.address = address;
  19.     }
  21.     private void method1() {
  22.         System.out.println("method1");
  23.     }
  25.     public void method2() {
  26.         System.out.println("method2");
  27.     }
  29.     protected void method3() {
  30.         System.out.println("method3");
  31.     }
  33.     void method4() {
  34.         System.out.println("method4");
  35.     }
  37.     public String method5(String ss) {
  38.         return ss;
  39.     }
  41.     @Override
  42.     public String toString() {
  43.         return "Student{" +
  44.                 "name='" + name + '\'' +
  45.                 ", age=" + age +
  46.                 ", address='" + address + '\'' +
  47.                 '}';
  48.     }
  49. }

反射的三种方式

  1. /**
  2.  * 反射的三种方式
  3.  */
  4. public class ReflectDemo {
  5.     public static void main(String[] args) throws ClassNotFoundException {
  6.         /**
  7.          * 第一种:最简洁,最方便   .Class
  8.          */
  9.         Class<Student> sc = Student.class;
  10.         System.out.println(sc);
  11.         //>>> class org.itheima_01.Student
  12.         Class<Student> sc1 = Student.class;
  13.         System.out.println(sc1);
  14.         System.out.println(sc==sc1);
  16.         /**
  17.          * 第二种:通过类方法的 getClass()
  18.          */
  19.         Student s = new Student();
  20.         Class<? extends Student> sc2 = s.getClass();
  21.         System.out.println(sc2);
  22.         /**
  23.          * 第三种:可配置,最灵活   Class.forName 需抛出ClassNotFoundException异常
  24.          */
  25.         Class<?> sc3 = Class.forName("org.itheima_01.Student");
  26.         System.out.println(sc3);
  27.     }
  28. }

通过反射 获取类构造方法,创建对象

  1. import java.lang.reflect.Constructor;
  2. import java.lang.reflect.InvocationTargetException;
  4. public class ReflectDemo01 {
  5.     public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
  6.         //获取所有的 公共构造方法  getConstructors
  7.         Class<?> sc = Class.forName("org.itheima_01.Student");
  8.         Constructor<?>[] constructors = sc.getConstructors();
  9.         for (Constructor c:constructors){
  10.             //System.out.println(c);
  11.         }
  12.         /*
  13.             >>> public org.itheima_01.Student(java.lang.String,int,java.lang.String)
  14.                 public org.itheima_01.Student()
  15.          */
  17.         //获取所有的构造方法 getDeclaredConstructors
  18.         Constructor<?>[] dc = sc.getDeclaredConstructors();
  19.         for (Constructor c:dc){
  20.             //System.out.println(c);
  21.         }
  22.         /**
  23.          * 通过反射创建对象
  24.          */
  25.         //公共无参
  26.         Constructor<?> con = sc.getConstructor(); //不写参数就是默认的无参构造方法
  27.         Object o = con.newInstance();
  28.         System.out.println(o);
  29.         //私有带参  编译时异常-报错:java.lang.NoSuchMethodException
  30.         /*Constructor<?> con1 = sc.getConstructor(String.class, String.class);
  31.         Object o1 = con1.newInstance("秦苒", "武汉");
  32.         System.out.println(o1);*/
  33.         //公共带参
  34.         Constructor<?> con2 = sc.getConstructor(String.class,int.class, String.class);
  35.         Object o2 = con2.newInstance("秦苒",18, "武汉");
  36.         System.out.println(o2);
  38.         /**
  39.          * 通过new关键字创建对象
  40.          */
  41.         //公共无参
  42.         Student s = new Student();
  43.         System.out.println(s);
  44.         //私有带参 运行时异常-报错:'Student(java.lang.String, java.lang.String)' has private access in 'org.itheima_01.Student'
  45.         /*Student s1 = new Student("林风","舟山");
  46.         System.out.println(s1);*/
  47.         //公共带参
  48.         Student s2 = new Student("林风",25,"舟山");
  49.         System.out.println(s2);
  50.     }
  51. }

暴力反射

  1. import java.lang.reflect.Constructor;
  2. import java.lang.reflect.InvocationTargetException;
  4. public class ReflectDemo02 {
  5.     public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InvocationTargetException, InstantiationException, NoSuchMethodException {
  6.         Class<?> c = Class.forName("org.itheima_01.Student");
  7.         //无法使用私有构造方法 私有报错:IllegalAccessException
  8.         Constructor<?> dc = c.getDeclaredConstructor(String.class, int.class, String.class);
  9.         Object o = dc.newInstance("陈尽", 21, "长春");
  10.         System.out.println(o);
  11.         //>>>Student{name='陈尽', age=21, address='长春'}
  13.         /**
  14.          * 暴力反射 setAccessible - 可访问私有构造方法
  15.          */
  16.         Constructor<?> con = c.getDeclaredConstructor(String.class, String.class);
  17.         con.setAccessible(true);  //取消访问检查
  18.         Object o1 = con.newInstance("青岚", "成都");
  19.         System.out.println(o1);
  20.         //>>> Student{name='青岚', age=0, address='成都'}
  21.     }
  22. }

反射获取成员变量

  1. import java.lang.reflect.Constructor;
  2. import java.lang.reflect.Field;
  3. import java.lang.reflect.InvocationTargetException;
  5. public class ReflectDemo03 {
  6.     public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
  7.         Class<?> c = Class.forName("org.itheima_01.Student");
  8.         /**
  9.          * 获取所有成员变量
  10.          */
  11.         Field[] dfs = c.getDeclaredFields();
  12.         for (Field f:dfs){
  13.             System.out.println(f);
  14.         }
  16.         Constructor<?> con = c.getConstructor();
  17.         Object o = con.newInstance();
  19.         /**
  20.          * 暴力私有变量访问  name
  21.          */
  22.         //方式一通用
  23.         Field name = c.getDeclaredField("name");
  24.         name.setAccessible(true);
  26.         Field address = c.getField("address");
  28.         Field age = c.getDeclaredField("age");
  30.         name.set(o,"张白亮");
  31.         age.set(o,18);
  32.         address.set(o,"长寿");
  33.         System.out.println(o);
  34.         //>>> Student{name='张白亮', age=18, address='长寿'}
  35.     }
  36. }

反射获取成员方法

  1. import java.lang.reflect.Constructor;
  2. import java.lang.reflect.InvocationTargetException;
  3. import java.lang.reflect.Method;
  5. public class ReflectDemo04 {
  6.     public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
  7.         Class<?> c = Class.forName("org.itheima_01.Student");
  8.         //所有-包括继承的方法
  9.         Method[] methods = c.getMethods();
  10.         for (Method m:methods){
  11.             //System.out.println(m);
  12.         }
  13.         //获取本类的所有方法,只是本类的
  14.         Method[] dms = c.getDeclaredMethods();
  15.         for (Method m:dms){
  16.             //System.out.println(m);
  17.         }
  18.         //创建对象
  19.         Constructor<?> con = c.getConstructor();
  20.         Object o = con.newInstance();
  21.         /**
  22.          * 调用方法
  23.          */
  24.         //private 修饰的需使用setAccessible暴力访问
  25.         Method method1 = c.getDeclaredMethod("method1");  //NoSuchMethodException
  26.         method1.setAccessible(true);
  27.         method1.invoke(o);
  28.         //只有public 修饰的才可通过getMethod 访问
  29.         Method method2 = c.getMethod("method2");  //NoSuchMethodException
  30.         method2.invoke(o);
  31.         //protected 修饰
  32.         Method method3 = c.getDeclaredMethod("method3");  //NoSuchMethodException
  33.         method3.invoke(o);
  34.         //默认修饰符
  35.         Method method4 = c.getDeclaredMethod("method4");  //NoSuchMethodException
  36.         method4.invoke(o);
  37.         //带参带返回值 的方法
  38.         Method method5 = c.getMethod("method5", String.class);
  39.         System.out.println(method5.invoke(o,"带参带返回值"));
  40.         String s = (String)method5.invoke(o, "我是参数");
  41.         System.out.println(s);
  42.     }
  43. }

反射越过泛型检查

  1. /**
  2.  * 通过反射越过泛型检查
  3.  */
  4. public class ReflectDemo05 {
  5.     public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
  6.         /**
  7.          * 通过反射在ArrayList<Integer>中添加一个字符串
  8.          */
  9.         ArrayList<Integer> arr = new ArrayList<>();
  10.         //arr.add("字符串");
  11.         arr.add(666);
  12.         Class<? extends ArrayList> aClass = arr.getClass();
  13.         Method add = aClass.getMethod("add", Object.class);
  14.         add.invoke(arr,"字符串");
  15.         System.out.println(arr);
  16.         //>>> [666, 字符串]
  17.     }
  18. }

反射读取配置文件

  1. import java.io.FileReader;
  2. import java.io.IOException;
  3. import java.lang.reflect.Constructor;
  4. import java.lang.reflect.InvocationTargetException;
  5. import java.lang.reflect.Method;
  6. import java.util.Properties;
  8. public class ReflectDemo06 {
  9.     public static void main(String[] args) throws IOException, ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
  10.         Teacher t = new Teacher();
  11.         t.study();
  13.         /**
  14.          * 通过反射读取配置文件调用函数,灵活性更高
  15.          * 配置 类名 与 方法名
  16.          * class.txt 文件内容如下:
  17.          * ClassName = org.itheima_01.Teacher
  18.          * MethodName = study
  19.          */
  20.         Properties properties = new Properties();
  21.         //Ctrl+Shift+C 复制文件绝对路径
  22.         FileReader fr = new FileReader("D:\\Graduation\\TestStudy\\src\\org\\itheima_01\\class.txt");
  23.         properties.load(fr);
  24.         fr.close();
  26.         String className = properties.getProperty("ClassName");
  27.         String methodName = properties.getProperty("MethodName");
  29.         Class<?> c = Class.forName(className);
  30.         Constructor<?> con = c.getConstructor();
  31.         Object obj = con.newInstance();
  33.         Method method = c.getMethod(methodName);
  34.         method.invoke(obj);
  36.     }
  37. }