嗯,我正在回答我自己的问题。
与C++不同,Java似乎对循环控制变量语句严格。以任何形式放入lambda函数都会导致错误。
因此,我所做的是使用单个for-loop和两个循环控制变量,像这样。
// Single for-loop
for (int i=1, j=2; i<10; i=(++j==10) ? i+1 : i, j=(j==10) ? 2 : j)
System.out.format("%dx%d=%2d%c",j,i,i*j,(j==9) ? '\n' : ' ');
因为它可以做与C++一样,我得到了好奇,并比较了C++源代码和他们的汇编代码这两种方法。
这里是C++代码(缩进为更好的可读性但是...),和
// 1. Using lambda function
for (int i=1; i<10;
[](int i) {for (int j=2; j<10; ++j)
printf("%dx%d=%2d ",j,i,i*j);}(i++))
printf("\n");
// 2. Using single for-loop
for (int i=1, j=2; i<10; i=(++j==10) ? i+1 : i, j=(j==10) ? 2 : j)
printf("%dx%d=%2d%c",j,i,i*j,(j==9) ? '\n' : ' ');
这里是组件(生成的NetBeans-MinGW的GCC)。 带有lambda函数的函数比具有多个三元运算符的单个for循环生成的代码更小。
! // 1. Using lambda function
! for (int i=1; i<10; [](int i) {for (int j=2; j<10; ++j) printf("%dx%d=%2d ",j,i,i*j);}(i++)) printf("\n");
main(int, char**)()
main(int, char**)+22: movl $0x1,-0xc(%ebp)
main(int, char**)+29: jmp 0x40172a <main(int, char**)+65>
main(int, char**)+31: movl $0x40a06f,(%esp)
main(int, char**)+38: call 0x408248 <printf(char const*, ...)>
main(int, char**)+43: mov -0xc(%ebp),%edx
main(int, char**)+46: incl -0xc(%ebp)
main(int, char**)+49: lea -0x15(%ebp),%eax
main(int, char**)+52: mov %edx,(%esp)
main(int, char**)+55: mov %eax,%ecx
main(int, char**)+57: call 0x4016a0 <operator()(int) const>
main(int, char**)+62: sub $0x4,%esp
main(int, char**)+65: cmpl $0x9,-0xc(%ebp)
main(int, char**)+69: setle %al
main(int, char**)+72: test %al,%al
main(int, char**)+74: jne 0x401708 <main(int, char**)+31>
!
! // 2. Using single for-loop
! for (int i=1, j=2; i<10; i=(++j==10) ? i+1 : i, j=(j==10) ? 2 : j) printf("%dx%d=%2d%c",j,i,i*j,(j==9) ? '\n' : ' ');
main(int, char**)+76: movl $0x1,-0x10(%ebp)
main(int, char**)+83: movl $0x2,-0x14(%ebp)
main(int, char**)+90: jmp 0x4017a8 <main(int, char**)+191>
main(int, char**)+92: cmpl $0x9,-0x14(%ebp)
main(int, char**)+96: jne 0x401752 <main(int, char**)+105>
main(int, char**)+98: mov $0xa,%eax
main(int, char**)+103: jmp 0x401757 <main(int, char**)+110>
main(int, char**)+105: mov $0x20,%eax
main(int, char**)+110: mov -0x10(%ebp),%edx
main(int, char**)+113: imul -0x14(%ebp),%edx
main(int, char**)+117: mov %eax,0x10(%esp)
main(int, char**)+121: mov %edx,0xc(%esp)
main(int, char**)+125: mov -0x10(%ebp),%eax
main(int, char**)+128: mov %eax,0x8(%esp)
main(int, char**)+132: mov -0x14(%ebp),%eax
main(int, char**)+135: mov %eax,0x4(%esp)
main(int, char**)+139: movl $0x40a071,(%esp)
main(int, char**)+146: call 0x408248 <printf(char const*, ...)>
main(int, char**)+151: incl -0x14(%ebp)
main(int, char**)+154: cmpl $0xa,-0x14(%ebp)
main(int, char**)+158: jne 0x40178f <main(int, char**)+166>
main(int, char**)+160: mov -0x10(%ebp),%eax
main(int, char**)+163: inc %eax
main(int, char**)+164: jmp 0x401792 <main(int, char**)+169>
main(int, char**)+166: mov -0x10(%ebp),%eax
main(int, char**)+169: mov %eax,-0x10(%ebp)
main(int, char**)+172: cmpl $0xa,-0x14(%ebp)
main(int, char**)+176: je 0x4017a0 <main(int, char**)+183>
main(int, char**)+178: mov -0x14(%ebp),%eax
main(int, char**)+181: jmp 0x4017a5 <main(int, char**)+188>
main(int, char**)+183: mov $0x2,%eax
main(int, char**)+188: mov %eax,-0x14(%ebp)
main(int, char**)+191: cmpl $0x9,-0x10(%ebp)
main(int, char**)+195: setle %al
main(int, char**)+198: test %al,%al
main(int, char**)+200: jne 0x401745 <main(int, char**)+92>
当然。你可以不使用换行符。 – NiematojakTomasz
你在这里有多个语句,你只是给了一个关于身份(或者换行符)的狗屎(像编译器一样)... – Paranaix
你可以在java中的“一行”中做任何事情。这是一种自由形式的语言,如C++ –