Java 8 Interface引入新特性- static method, default method

ゝ一纸荒年。 2024-03-22 20:13 66阅读 0赞

## default method ##

### 定义default方法 ###

public interface Interface1 {
        
    
        void method1(String str);
    
        default void log(String str){
        
            System.out.println("I1 logging::"+str);
        }
    }

### default方法使用 ###

public class Interface1Impl implements Interface1 {
        
    
        @Override
        public void method1(String str) {
        
        }
    
        public static void main(String[] args) {
        
            Interface1Impl interface1Impl = new Interface1Impl();
            interface1Impl.log("abc");
        }
    }
    
    执行结果：
    I1 logging::abc

### 方法名冲突场景 ###

public interface Interface2 {
        
    
        void method2();
    
        default void log(String str){
        
            System.out.println("I2 logging::"+str);
        }
    
    }

public class MyClass implements Interface1, Interface2 {
        
        @Override
        public void method2() {
        
        }
        @Override
        public void method1(String str) {
        
        }
        @Override
        public void log(String str) {
        
            System.out.println("MyClass logging::" + str);
            Interface1.super.log(str);
        }
        public static void main(String[] args) {
        
            MyClass myClass = new MyClass();
            myClass.log("abc");
        }
    }
    
    执行结果：
    MyClass logging::abc
    I1 logging::abc

## static method ##

### 定义static方法 ###

public interface Interface3 {
        
        void method3();
        
        default void print(String str) {
        
            if (!isNull(str))
                System.out.println("Interface3 Print: " + str);
        }
        
        static boolean isNull(String str) {
        
            System.out.println("Interface Null Check: " + str);
            return str == null;
        }
    }

### static方法使用 ###

public class Interface3Impl implements Interface3 {
        
        @Override
        public void method3() {
        
        }
        
        public boolean isNull(String str) {
        
            System.out.println("Interface3Impl Null Check: " + str);
            return str == null;
        }
        
        public static void main(String args[]) {
        
            Interface3Impl obj = new Interface3Impl();
            obj.print("");
            obj.isNull("abc");
            Interface3.isNull("123");
        }
    }
    
    执行结果：
    Interface Null Check: 
    Interface3 Print: 
    Interface3Impl Null Check: abc
    Interface Null Check: 123

## 参考 ##

[Java 8 Interface Changes - static method, default method][Java 8 Interface Changes - static method_ default method]

[Java 8 Interface Changes - static method_ default method]: https://www.digitalocean.com/community/tutorials/java-8-interface-changes-static-method-default-method