public class WordConversion {

//大写转小写

public static String toLowerCase(String str) {

char [] a = str.toCharArray();

for (int i = 0;i < str.length();i++) {

if (a[i] >= 65 && a[i]<= 90) {

a[i] = (char)(a[i] + 32);

}

}

return new String(a);

}

//小写转大写

public static String toHigherCase(String str) {

char [] a = str.toCharArray();

for (int i = 0;i < str.length();i++) {

if (a[i] >= 97 && a[i]<= 122) {

a[i] = (char)(a[i] - 32);

}

}

return new String(a);

}

public static void main(String[]args){

String str = "Hello World";

System.out.println("大写转小写:"+toLowerCase(str));

System.out.println("小写转大写:"+toHigherCase(str));

}

}