Summary IEB IT Java Notes

Java Coding Notes

Typecasting
String → int
int num = Integer.parseInt (Str);

String → double
double num = Double.parseDouble (Str);

double → int
int intNum = (int) dblNum;

int → double
double dblNum = intNum;

int → char (Converts to ASCII Value)
char ch = (char) intNum;

char → int (Converts to ASCII Number)
int intNum = (int) ch;

int → String
String str = “ ” + intNum;

double → String
String str = “ ” + dblNum;

String → char
char ch = str.charAt(index);
.toUpperCase() or .toLowerCase()

char → String
String str = “ ” + ch;

Formatting and Arithmetic
Constants / Finals:
public/private static final <type> <name> = <value>;

Useful Tools:
String.format("%.2f", <double>); round off to 2 decimals
System.arraycopy (<sourceArr>, <sourcePos>, <destArr>, <destPos>, <size>); copy
part of an array into another array

Math Class:
Square Root: Math.sqrt (x)
Raise to Power: Math.pow (x, exponent)
Round off: Math.round (x)
Absolute Value: Math.abs (-x)
Random Number: Math.random () * (max) + (start)

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, Java Coding Notes

Array Handling
Declaring an array:
[variable type] [variable name] [] = new [variable type] [size];


Inputting an array with a known amount of values:
int array [] = new int [10];
for (int loop = 0; loop < 10; loop++){
array [loop] = [input method];
}//end for loop

Inputting an array with an unknown amount of values:
int count = 0;
String wrdArr [] = new String [10]
wrdArr [count] = [input method];
while (!wrdArr [count].equalsIgnoreCase (“stop”)){
count++;
wrdArr [count] = [input method]
}//end while loop

Displaying an array:
for (int loop = 0; loop < [size]; loop++){
System.out.println (array [loop]);
}//end for loop


Inserting into an array:
public void shiftRight (int insertPos, String newString){
for (int loop = size; loop > insertPos; loop--){
stArr [loop + 1] = stArr [loop];
}//end for loop
stArr [insertPos] = newString;
size++;
}//shiftRight insert method

Deleting from an array
public void shiftLeft (int removePos){
for (int loop = removePos; loop < size; loop++){
stArr [loop] = stArr [loop + 1];
}//end for loop
size--;
}//shiftLeft delete method
Or you can just override the deleted array index with the last index and call a
sort method.



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