我有这段代码,其中有两个循环“i”和“j”。
'j' 是内循环变量,它应该在外循环的单次运行中运行 999 到 100。
但它随机运行,就像, 假设 i=999
j=912
j=911
j=910
j=909
j=908
j=907
j=906
然后突然内循环退出,从外循环递减1并使
i=998
然后开始'j'循环
j=908
j=907
j=906
j=905
j=906
j=905
j=904
j=903
j=902
然后退出内循环................................
int product=0;
mainloop:
for(int i=999;i>99;i--){
for(int j=999;j>99;j--){
boolean flag= doSomething(i*j);
if(flag){
product=i*j;
System.out.println("Digits are: "+i+" and "+j);
break mainloop;
}
}
}
public boolean doSomething(int product){
String original= Integer.toString(product),reverse="";
int length = original.length();
for ( int i = length - 1; i >= 0; i-- )
reverse = reverse + original.charAt(i);
return (original.equals(reverse));
}
为什么会这样?为什么内循环没有完成从 999 到 100 的循环?
编辑: 要清楚,只有当 j=913 和 i=993 时,'flag' 才会为真,这是此时循环不会中断的主要问题,因为 'j' 永远不会达到 913,但它会随机生成number.Moreover 'break' 不仅会破坏内循环,还会破坏主循环。
您在内部循环中有一个条件 -
if(flag)
- 如果为真,则从该循环中断。这就是内循环没有完成的原因。它不会“随机”运行。它的行为取决于doSomething(i*j)
方法调用的结果。
使用一些额外的调试打印和你声称拥有的
doSomething
的实现来运行你的代码:
int product=0;
mainloop:
for(int i=999;i>99;i--){
System.out.print ("\n"+i+":");
for(int j=999;j>99;j--){
System.out.print (j+",");
boolean flag= doSomething(i*j);
if(flag){
product=i*j;
System.out.println("\nDigits are: "+i+" and "+j);
break mainloop;
}
}
}
public static boolean doSomething(int k)
{
return k == 913*993;
}
给出预期的输出:
999:999,998,997,996,995,994,993,992,991,990,989,988,987,986,985,984,983,982,981,980,...,120,119,118,117,116,115,114,113,112,111,110,109,108,107,106,105,104,103,102,101,100,
998:999,998,997,996,995,994,993,992,991,990,989,988,987,986,985,984,983,982,981,980,...,120,119,118,117,116,115,114,113,112,111,110,109,108,107,106,105,104,103,102,101,100,
997:999,998,997,996,995,994,993,992,991,990,989,988,987,986,985,984,983,982,981,980,...,120,119,118,117,116,115,114,113,112,111,110,109,108,107,106,105,104,103,102,101,100,
996:999,998,997,996,995,994,993,992,991,990,989,988,987,986,985,984,983,982,981,980,...,120,119,118,117,116,115,114,113,112,111,110,109,108,107,106,105,104,103,102,101,100,
995:999,998,997,996,995,994,993,992,991,990,989,988,987,986,985,984,983,982,981,980,...,120,119,118,117,116,115,114,113,112,111,110,109,108,107,106,105,104,103,102,101,100,
994:999,998,997,996,995,994,993,992,991,990,989,988,987,986,985,984,983,982,981,980,...,120,119,118,117,116,115,114,113,112,111,110,109,108,107,106,105,104,103,102,101,100,
993:999,998,997,996,995,994,993,992,991,990,989,988,987,986,985,984,983,982,981,980,979,978,977,976,975,974,973,972,971,970,969,968,967,966,965,964,963,962,961,960,959,958,957,956,955,954,953,952,951,950,949,948,947,946,945,944,943,942,941,940,939,938,937,936,935,934,933,932,931,930,929,928,927,926,925,924,923,922,921,920,919,918,917,916,915,914,913,
Digits are: 993 and 913
编辑,当 i==995 和 j==583 时,您发布的
doSomething
返回 true。那就是你打破循环的时候。