简单的题目,同时满足三个条件即可。
注意1: Integer.toBinaryString(int num)返回的是String类型
new StringBuilder(String str)返回的是StringBuilder类型,此类型下面有翻转方法reverse(),但String的equal()方法的参数是String类型的,故需要把StringBuilder类型用toString()转化成String类型。
注意2:
把int型转化成String类型有3种方法:
1) String str = ""+num;
2) String str = Integer.toString(num);
3) String str = String.valueOf(num);
byte, short, long, float, double, boolean 转化成String类型同理,此处不再赘述!
package InterestingAlgorithmPazzles; /* * 回文十进制数 * 求十进制、八进制、二进制表示都是回文数的大于十进制数10的最小值 * * 答案是 585 (八进制1111)(二进制1001001001) * * Java进制转换接口:Integer类下 * toBinaryString() , toOctalString() , toHexString() * * 注意:将字符串翻转可以new一个StringBuffer()对象,让后调用其reverse()方法,再调用其toString()方法转成字符串类型 * */ public class Main001 { public static void main(String[] args) { // int num = 585; for(int num=11; ;++num) { //// System.out.println(new StringBuilder(Integer.toBinaryString(num)).reverse().toString()); //// System.out.println(Integer.toBinaryString(num).equals(Integer.toBinaryString(num))); if(Integer.toBinaryString(num).equals(new StringBuilder(Integer.toBinaryString(num)).reverse().toString())==true && Integer.toOctalString(num).equals(new StringBuilder(Integer.toOctalString(num)).reverse().toString())==true && (new StringBuilder(""+num).reverse().toString().equals(new StringBuilder(""+num).toString())==true) ) { System.out.println(num); break; } // System.out.println(Integer.toBinaryString(num).equals(new StringBuilder(Integer.toBinaryString(num)).reverse().toString())); // System.out.println(Integer.toOctalString(num).equals(new StringBuilder(Integer.toOctalString(num)).reverse().toString())); // System.out.println(new StringBuilder(""+num).reverse().toString().equals(new StringBuilder(""+num))); // String mid = new StringBuilder(""+num).reverse().toString(); // System.out.println(mid.equals(new StringBuilder(""+num).toString())); // System.out.println(new StringBuilder(""+num)); } } }