java syntax notes copy
* There is no "get(int index)" method for
hashSet in java
1) Convert string to char array:
char[] ch = nameStr.toCharArray();
ch t = ch[0];
2) Convert char to string:
Use StringBuilder.
char ch = 'A';
String str = "" + ch;
3) set char value to empty or null.
This will set value to '\u0000'.
If you don't initialize char[] , all values in it will be equal to '\u0000'.
You can check if (char[4] == Character.MIN_VALUE)
chArr[2] = Character.MIN_VALUE;
4) If you want to just reverse the original
arraylist without saving original copy:
Collections.reverse(origArrayList);
>>>> If you want to store both original and reversed arraylist :
ArrayList reversed = new ArrayList() ;
for ( int i = orig.size() - 1 ; i >= 0 ; i-- )
{
Object obj = orig.get( i ) ;
reversed.add( obj ) ;
}
5)
// create an array of strings
String a[] = new String[]{"abc","klm","xyz","pqr"};
List list1 = Arrays.asList(a);
Or
List list1 = Arrays.asList(3, 2, 4);
6) sort an array:
http://www.geeksforgeeks.org/arrays-sort-in-java-with-examples/
(http://www.geeksforgeeks.org/arrays-sort-in-java-with-examples/)
int [] arr = { 13 , 7 , 6 , 45 , 21 , 9 , 101 , 102 };
Arrays.sort(arr);
// Note that we have Integer here instead of
// int[] as Collections.reverseOrder doesn't
// work for primitive types.
Integer[] arr = { 13 , 7 , 6 , 45 , 21 , 9 , 2 , 100 };
// Sorts arr[] in descending order
Arrays.sort(arr, Collections.reverseOrder());
7)convert char[] to string:
String s = "str";
char[] cArr = s.toCharArray();
String ss = String.valueOf(cArr);
8)
str.charAt(int index);
9)
int[] nums = {-2147483648,-2147483648,-2147483648,-2147483648,1,1,1};
Integer max3 = null;
for(Integer n : nums){
if(n.equals(max3) ){ // IMP********
}