Java 스터디 강의자료 - 1차시
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This document contains code examples demonstrating Java programming concepts like: - Printing output to the console - Declaring and initializing variables of different primitive data types - Handling errors from incompatible type conversions - Using loops and conditional statements like for and if - Performing mathematical operations like square roots - Taking user input using Scanner - Concatenating Strings - Declaring and initializing arrays - Scope of variables declared within blocks
![class Test {
public static void main(String[] args) {
System.out.println("Hello world!");
}
}
$ javac test.java
$ java Test
Hello world!](https://image.slidesharecdn.com/javastudy1-180304160249/85/Java-1-8-320.jpg)
![int a;
int b = 1;
int c, d, e = 2;
double f = 3.12312;
char g = 'A';
[ ] [ ];
[ ] [ ] = [ ];
[ ] [1 ], [2 ];](https://image.slidesharecdn.com/javastudy1-180304160249/85/Java-1-11-320.jpg)
![import java.util.Scanner;
class Test {
public static void main(String[] args) {
int x;
Scanner input = new Scanner(System.in);
x = input.nextInt();
System.out.println(" : " + x);
}
}
123
: 123](https://image.slidesharecdn.com/javastudy1-180304160249/85/Java-1-21-320.jpg)
![// declares an array of integers
int[] anArray;
// allocates memory for 10 integers
anArray = new int[10];
anArray[0] = 100;
anArray[1] = 200;
System.out.println("Element at index 0: " + anArray[0]);
System.out.println("Element at index 1: " + anArray[1]);
System.out.println(anArray.length);](https://image.slidesharecdn.com/javastudy1-180304160249/85/Java-1-23-320.jpg)
Java 스터디 강의자료 - 1차시
- 8. class Test { public static void main(String[] args) { System.out.println("Hello world!"); } } $ javac test.java $ java Test Hello world!
- 9. $ javac < > $ java < >
- 11. int a; int b = 1; int c, d, e = 2; double f = 3.12312; char g = 'A'; [ ] [ ]; [ ] [ ] = [ ]; [ ] [1 ], [2 ];
- 12. float ave = 5.16F; long id = 2147483648L; char ko = ' '; boolean flag = true;
- 14. System.out.println(5 / 2); int a = 1; float b = a; double c = b; float ave = 3.75F; int num = (int)ave;
- 15. int ii = 3.5; // 7 float f = 3.333; // 9 float ff = 3; // 10 char c = 'A'; // 12 char cc = 65; // 13 boolean b = 1; // 15 test.java:7: error: incompatible types: possible lossy conversion from double to int int ii = 3.5; ^ test.java:9: error: incompatible types: possible lossy conversion from double to float float f = 3.333; ^
- 17. int i, sum = 0; for (i = 1; i <= 10; i++) { if (i % 2 == 0) sum += i; } System.out.println("Sum: " + sum);
- 18. int i = 2; double r = Math.sqrt(i); System.out.print("The square root of "); System.out.print(i); System.out.print(" is "); System.out.print(r); System.out.println("."); The square root of 2 is 1.4142135623730951.
- 19. int i = 5; double r = Math.sqrt(i); System.out.println("The square root of " + i + " is " + r + "."); The square root of 5 is 2.23606797749979.
- 20. int i = 2; double r = Math.sqrt(i); System.out.format("The square root of %d is %f.%n", i, r); The square root of 2 is 1.414214.
- 21. import java.util.Scanner; class Test { public static void main(String[] args) { int x; Scanner input = new Scanner(System.in); x = input.nextInt(); System.out.println(" : " + x); } } 123 : 123
- 22. String s = "this is a string"; String s1 = "cat"; String s2 = s1 + " dog"; System.out.println(s2);
- 23. // declares an array of integers int[] anArray; // allocates memory for 10 integers anArray = new int[10]; anArray[0] = 100; anArray[1] = 200; System.out.println("Element at index 0: " + anArray[0]); System.out.println("Element at index 1: " + anArray[1]); System.out.println(anArray.length);
- 25. int v = 0; for (int i = 1; i <= 3; i++) { int v = 10; v += i; System.out.format("i=%2d, v=%dn", i, v); } System.out.format("Outer v=%dn", v); i= 1, v=? i= 2, v=? i= 3, v=? Outer v=?