字符串或者数组的循环左移或右移（不开辟额外的空间存放中间值）

int a=10;
int b=15;
a = a + b;
b = a - b;
a = a - b;

public class LeftRotateString {
public static void main(String[] args) {
System.out.println(change("abcdefgh".toCharArray(),3));
}

public static char[] change(char[] c,int k){
for(int i=0;i<k/2;i++){
/*c[i]^=c[j]^=c[i]^=c[j];*/
int j = k-i-1;
c[i]=(char) (c[i]+c[j]);
c[j]=(char) (c[i]-c[j]);
c[i]=(char) (c[i]-c[j]);

}
for(int n=0;n<(c.length-k)/2;n++){
int j=c.length-1-n;
int i=k+n;
c[i]=(char) (c[i]+c[j]);
c[j]=(char) (c[i]-c[j]);
c[i]=(char) (c[i]-c[j]);
}
for(int i=0;i<c.length/2;i++){
int j=c.length-1-i;
c[i]=(char) (c[i]+c[j]);
c[j]=(char) (c[i]-c[j]);
c[i]=(char) (c[i]-c[j]);
}
return c;
}
}