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锁定老帖子 主题：奇怪的 switch() case 题目
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发表时间：2009-03-30
最后修改：2009-03-30
寻梦之龙 写道 duduli 写道 public static void testCase(int x) {
switch (x) { case 1: System.out.println("is 1"); break; case 2: case 3: case 4: System.out.println("is 2 3 4"); break; default: x = x>4?5:-1; case 5: System.out.println("big 4"); break; case -1: System.out.println("less 1"); } } Head First设计模式■ 群共同努力 Ta的运行不正确 正确运行: public class SpecialSwitch { public static void main(String[] args){ int data[]=new int[]{5}; int len=data.length; for(int i=0;i<len;i++){ testCase(data[i]); } } public static void testCase(int x) { int data=x; System.out.println(data); switch (data) { case 1: System.out.println("is 1"); break; case 2: case 3: case 4: System.out.println("is 2 3 4"); break; default: data = data>4?5:-1; case -1: System.out.println("less 1"); break; case 5: System.out.println("big 4"); break; } } } 没理解switch的用法，就乱写，换了位置和没换都一样有问题啊。不相信，你测试下6，结果是less 1 default: data = data>4?5:-1; case -1: System.out.println("less 1"); break; case 5: System.out.println("big 4"); break; 这个其实了解一下switch语句用if else来实现就知道了。 始终是判断data的，如果找不到，就按default处理，如果default没有break跳出语句，那么他后面的语句将依次执行。 所以如果data的值不是{1,2,3,4,5,-1}中一个的话，都会执行接下来的case语句，打印less 1。 然后break跳出，所以case 5语句始终是没有执行到的。 你换个位置，只不过是把case 5始终执行，case -1 永远不执行罢了。 其实和 switch(1){ case 1 : System.out.println(1); case 2 : System.out.println(2); break; } 打印 1 2 一样的道理。 |
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发表时间：2009-04-02
最后修改：2009-04-03
建立一个公式吧
Y=X<1:0?(X<5?X:5) 这样不知道可以不?没用过嵌套三元表达式 |
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发表时间：2009-09-15
纯路过。。。
def bt_case(x) infinity = -1/0.0 case x when (infinity...1) then puts "less then 1" when 1 then puts "x is 1" when (2..4) then puts "one of 2 3 4" when (5..-infinity) then puts " bigger then 4" end end 结果： irb(main):065:0> bt_case(1) x is 1 => nil irb(main):066:0> bt_case(0) less then 1 => nil irb(main):067:0> bt_case(-1) less then 1 => nil irb(main):068:0> bt_case(2) one of 2 3 4 => nil irb(main):069:0> bt_case(3) one of 2 3 4 => nil irb(main):070:0> bt_case(5) bigger then 4 => nil irb(main):071:0> bt_case(8) bigger then 4 => nil irb(main):072:0> bt_case(8.5) bigger then 4 => nil irb(main):073:0> |
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发表时间：2009-09-15
ninecat 写道 都不对,题目很明显只让用switch 而不能用其他的判断比如if\3元表达式(for 和while应该也不算)
看看这个怎么样:
public class Switch {
public static void main(String[] args) {
int x =5;
try {
switch ((x-1)/x) {
case 1:
case 2:
System.out.println("x is less than 1");
break;
default:
switch ((x+4)/x) {
case 5:
System.out.println("x is 1");
break;
case 3:
case 2:
System.out.println("x is 2,3,4");
break;
case 1:
System.out.println("x is greater than 4");
break;
}
break;
}
} catch (Exception e) {
System.out.println("x is less than 1");
}
}
}
 魔幻数字。。。。
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发表时间：2009-09-16
我的处女帖就给了你吧！
以下是我的除了switch case以外没有其他判断的实现。
public class Switch {
public static void main(String[] args) {
for (int x = -10; x < 10; x++) {
System.out.print(x);
switch (x) {
case 1:
System.out.println(" is 1");
break;
case 2:
case 3:
case 4:
System.out.println(" is 2,3 or 4");
break;
default:
switch (-x % (x - 1)) {
case -1:
System.out.println(" is greater than 4");
break;
default:
System.out.println(" is less than 1");
break;
}
break;
}
}
}
}
结果 -10 is less than 1 -9 is less than 1 -8 is less than 1 -7 is less than 1 -6 is less than 1 -5 is less than 1 -4 is less than 1 -3 is less than 1 -2 is less than 1 -1 is less than 1 0 is less than 1 1 is 1 2 is 2,3 or 4 3 is 2,3 or 4 4 is 2,3 or 4 5 is greater than 4 6 is greater than 4 7 is greater than 4 8 is greater than 4 9 is greater than 4 |
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