字符串翻转

1.循环便利字符串，字符串倒置

String str = "zhangsan";
StringBuilder sb = new StringBuilder();
int len = str.length();
for(int i=len;i>0;i--){
sb.append(str.substring(i-1,i));
}

2.和第一种类似，也是便利，只是把String字符串转化为char数组

String str = "zhangsan";
char[] c = str.toCharArray();
int l = c.length;
char[] newStr = new char[l];
for(int i=0;i<l;i++){
newStr[i] = c[l-i-1];
}
System.out.println(new String(newStr));

3.和第二种方法类似，但是从前后同时进行，加快速度

String str = "zhangsan";
char[] c = str.toCharArray();
int l = c.length;
for(int i=0;i<l/2;i++){
char t = c[i];
System.out.println(t);
c[i] = c[l-i-1];
c[l-i-1] = t;
}
system.out.println(new String(c));