lambda expression written
lambda must have an interface, and the interface is only an abstract method
lambda consists of three parts:
1. Parameter
2 .->
3. snippet
format is as follows:
(Parameter Type name) -> {} snippet
Where: parameter type parameter name is not required, if there are multiple, separated by commas. -> is a lambda syntax specific requirements
Shorthand rule of lambda
1: Parameter Type in parentheses may be omitted.
2: If the parentheses and only one parameter, the parentheses may be omitted.
3: If the braces and only one statement, regardless of whether there is a return value, you can omit the braces, return keywords and semicolons.
Difference between traditional writing of code and lambda expressions
package cn.hp.lambda;
public class Lamdba {
public static void main(String[] args) {
new Thread(new Runnable() {
/**
* 采用 接口方式启动线程对象
* 1:必须new 接口对象Runnable
* 2：必须重写run方法
* 3：必须调用start() 启动线程
*/
@Override
public void run() {
System.out.println("传统启动线程方法");
}
}).start();
/**
*lamdba表达式写法
*不必new接口对象
*不必重新run方法
*/
new Thread(()->{System.out.println("传统启动线程方法");}).start();
//()代表run函数 进一步简写省略（大括号：{}）
new Thread(()->System.out.println("传统启动线程方法")).start();
}
}
Parentheses only one parameter, parentheses may be omitted
package cn.hp.lambda;
/**
* 测试
* 小括号仅有一个参数，小括号可以省略
*/
public interface Lamdba4 {
void test(String str);
}
class Lamdba4Impl {
public static void main(String[] args) {
Lamdba4 l4 =(ss)->{ System.out.println(ss);};
//简写省略 大括号
Lamdba4 l5 =ss->System.out.println(ss);
//调用方法
l4.test("hello world");
}
}
No reference no return Lamdba value of the expression
package cn.hp.lambda;
/**
* 无参无返回值 指的是，接口中的方法
*/
public interface Lamdba2 {
void pint();//提供一个无参无返回值的 方法
}
class Lamdba2Impl{
public static void main(String[] args) {
/**
* 提供了一个接口对象 l2
* 等号右侧 第一个()代表pint()
*/
Lamdba2 l2 = ()->{System.out.println("打印字字符串");};
//进一步简写 省略大括号
Lamdba2 l2=()-> System.out.println("打印字字符串");
l2.pint();//调用pint方法
}
}
There have Lamdba expression returns parameter values
lambda requirements, the method includes a parameter or variable type must lambda corresponding interface type to use as the lambda interface instance
package cn.hp.lambda;
/**
* 有参有返回值
*/
public interface Lamdba3 {
int add (int x,int y);
}
class Lamdba3Impl{
public static void main(String[] args) {
textAdd((int a,int b)->{return a+b;});
//进一步简写 省略参数类型 return 和大括号
textAdd((a,b)->a+b);
}
//建立与接口的联系
public static void textAdd(Lamdba3 l3){
int result=l3.add(10,13);
System.out.println("求和"+result);
}
}
