Lambda 表达式介绍和底层实现分析

(parameters) -> expression或 (parameters) ->{ statements; }

(int x, int y) -> x + y() -> 42(String s) -> { System.out.println(s); }

public interface MyFunctionInterface<T> {    public T getValue(T t);}

public class MyFunctionInterfaceTest {    public static void main(String[] args) {        testMethod("   aaaa  ", s -> s.trim());        testMethod("   aaaa  ", s -> s.trim().toUpperCase());    }
    public static void testMethod(String str,     MyFunctionInterface<String> functionInterface) {        System.out.println(functionInterface.getValue(str));    }}

aaaaAAAA

public interface MyFunctionInterface<T> {    public T getValue(T t);    public T returnValue(T t);}

@FunctionalInterfacepublic interface MyFunctionInterface<T> {
    public T getValue(T t);
    default void defaultMethod() {        System.out.println("this is default method");    }
    static void staticMethod() {        System.out.println("this is static method");    }

    public boolean equals(Object obj);}

// access flags 0x100Aprivate static synthetic lambda$main$1(Ljava/lang/String;)Ljava/lang/String; L0  LINENUMBER 6 L0  ALOAD 0  INVOKEVIRTUAL java/lang/String.trim ()Ljava/lang/String;  INVOKEVIRTUAL java/lang/String.toUpperCase ()Ljava/lang/String;  ARETURN L1  LOCALVARIABLE s Ljava/lang/String; L0 L1 0  MAXSTACK = 1  MAXLOCALS = 1
// access flags 0x100Aprivate static synthetic lambda$main$0(Ljava/lang/String;)Ljava/lang/String; L0  LINENUMBER 5 L0  ALOAD 0  INVOKEVIRTUAL java/lang/String.trim ()Ljava/lang/String;  ARETURN L1  LOCALVARIABLE s Ljava/lang/String; L0 L1 0  MAXSTACK = 1  MAXLOCALS = 1}

(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;

java/lang/invoke/LambdaMetafactory.metafactory(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;

public static CallSite metafactory(MethodHandles.Lookup caller,                                   String invokedName,                                   MethodType invokedType,                                   MethodType samMethodType,                                   MethodHandle implMethod,                                   MethodType instantiatedMethodType)        throws LambdaConversionException {    AbstractValidatingLambdaMetafactory mf;    mf = new InnerClassLambdaMetafactory(caller, invokedType,                                         invokedName, samMethodType,                                         implMethod, instantiatedMethodType,                                         false, EMPTY_CLASS_ARRAY, EMPTY_MT_ARRAY);    mf.validateMetafactoryArgs();    return mf.buildCallSite();}