Java Data Types
- String
- int
- double
- boolean
- true
- false
Primitive types such as int, float, boolean, etc. Or reference types, such as strings, arrays, or objects.
42 - int
1_234 - int
true, false - boolean
"string" - string in double quotes
'x' - char in single quotes
'x' == "x" - execption as cannot compare char with string.
"abc".getClass() works and prints class java.lang.String, but does not work on any of the other data types
public class CheckDataTypes {
public static void main(String[] args) {
// https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html
System.out.println("Checking Data Types");
String h = "Hello";
String w = "World";
System.out.println(h); // Hello
System.out.println(w); // World
String full = h + " " + w;
System.out.println(full); // Hello World
// int is 32 bit sigend between -2^31 and 2^31-1
int val1 = 19;
int val2 = 23;
int val3 = val1 + val2;
System.out.println(val3); // 42
// double 64-bit IEEE 754 floating point.
double db1 = 19.3;
double db2 = 22.7;
double db3 = db1 + db2;
System.out.println(db3); // 42.0
boolean b = true;
System.out.println(b); // true
b = ! b;
System.out.println(b); // false
if (!b) {
System.out.println("yeah");
System.out.println("works");
}
// Actually if there is only a single statement in the block you don't even need the curly braces, but I would recommend this practice:
if (!b)
System.out.println("this too");
// because of this:
if (b)
System.out.println("in condition");
System.out.println("NOT in condition"); // this is not inside the condition even though the indentation seems to suggest that.
}
}
javac CheckDataTypes.java
java CheckDataTypes
Checking Data Types
Hello
World
Hello World
42
42.0
true
false
yeah
works
this too
NOT in condition