tour de java.lang

1.Tujuan
Menggunakan class-class Java yang telah ada
● Math
● String
● StringBuffer
● Wrapper
● Process
● System
2.Percobaan
Percobaan 1 : Demo Method – Method dari Class Math
public class Java_Lang_MathDemo {
public Java_Lang_MathDemo() {
}
public static void main(String args[]) {
System.out.println(“absolute value of -5: ” + Math.abs(-5));
System.out.println(“absolute value of 5: ” + Math.abs(-5));
System.out.println(“random number(max value is 10): “Math.random()*10);
System.out.println(“max of 3.5 and 1.2: ” + Math.max(3.5, 1.2));
System.out.println(“min of 3.5 and 1.2: ” + Math.min(3.5, 1.2));
System.out.println(“ceiling of 3.5: ” + Math.ceil(3.5));
System.out.println(“floor of 3.5: ” + Math.floor(3.5));
System.out.println(“e raised to 1: ” + Math.exp(1));
System.out.println(“log 10: ” + Math.log(10));
System.out.println(“10 raised to 3: ” + Math.pow(10,3));
System.out.println(“rounded off value of pi: ” + Math.round(Math.PI));
System.out.println(“square root of 5 = ” + Math.sqrt(5));
System.out.println(“10 radian = ” + Math.toDegrees(10) + ” degrees”);
System.out.println(“sin(90): ” + Math.sin(Math.toRadians(90)));
}
}
Distributed by Meruvian Education
Output Percobaan 1
Percobaan 2 : String Constructor Demo
public class Java_Lang_StringConstructorDemo {
public Java_Lang_StringConstructorDemo() {
}
public static void main(String args[]) {
String s1 = new String(); // creates an empty string
char chars[] = { ‘h’, ‘e’, ‘l’, ‘l’, ‘o’};
String s2 = new String(chars); // s2 = “hello”;
byte bytes[] = { ‘w’, ‘o’, ‘r’, ‘l’, ‘d’ };
String s3 = new String(bytes); // s3 = “world”
String s4 = new String(chars, 1, 3);
String s5 = new String(s2);
String s6 = s2;
System.out.println(s1);
System.out.println(s2);
System.out.println(s3);
System.out.println(s4);
System.out.println(s5);
System.out.println(s6);
}
}
Distributed by Meruvian Education
Output Percobaan 2 :
Percobaan 3 : Demo Method Class String
Output Percobaan 3 :
Distributed by Meruvian Education
Percobaan 4 : Demo Method Class String Buffer
public class Java_Lang_StringBufferDemo {
public Java_Lang_StringBufferDemo() {
}
public static void main(String args[]) {
StringBuffer sb = new StringBuffer(“Jonathan”);
System.out.println(“sb = ” + sb);
System.out.println(“capacity of sb: ” + sb.capacity());
System.out.println(“append \’O\’ to sb: ” + sb.append(“O”));
System.out.println(“sb = ” + sb);
System.out.println(“3rd character of sb: ” + sb.charAt(2));
char charArr[] = “Hi XX”.toCharArray();
sb.getChars(0, 2, charArr, 3);
System.out.print(“getChars method: “);
System.out.println(charArr);
System.out.println(“Insert \’jo\’ at the 3rd cell: ” + sb.insert(2, “jo”));
System.out.println(“Delete \’jo\’ at the 3rd cell: ” + sb.delete(2,4));
System.out.println(“length of sb: ” + sb.length());
System.out.println(“replace: ” + sb.replace(3, 9, ” Ong”));
System.out.println(“substring (1st two characters): ” + sb.substring(0, 3));
System.out.println(“implicit toString(): ” + sb);
}
}
Output Percobaan 4 :
Distributed by Meruvian Education
Percobaan 5 : Class Boolean Wrapper
public class Java_Lang_BooleanWrapper {
public Java_Lang_BooleanWrapper() {
}
public static void main(String args[]) {
boolean booleanVar = 1>2;
Boolean booleanObj = new Boolean(“TRue”);
Boolean booleanObj2 = new Boolean(booleanVar);
System.out.println(“booleanVar = ” + booleanVar);
System.out.println(“booleanObj = ” + booleanObj);
System.out.println(“booleanObj2 = ” + booleanObj2);
System.out.println(“compare2wrapperobjects:” + booleanObj.equals(booleanObj2));
booleanVar = booleanObj.booleanValue();
System.out.println(“booleanVar = ” + booleanVar);
}
}
Output Percobaan 5 :
Distributed by Meruvian Education
Percobaan 6 : Class Runtime – Membuka Registry Editor
public class Java_Lang_RuntimeDemo {
public Java_Lang_RuntimeDemo() {
}
public static void main(String args[]) {
Runtime rt = Runtime.getRuntime();
Process proc;
try {
proc = rt.exec(“regedit”);
proc.waitFor(); //try removing this line
} catch (Exception e) {
System.out.println(“regedit is an unknown command.”);
}
}
}
Output Percobaan 6 :
Distributed by Meruvian Education
Percobaan 7 : Demo Class System
import java.io.*;
public class Java_Lang_SystemDemo {
public Java_Lang_SystemDemo() {
}
public static void main(String args[]) throws IOException {
int arr1[] = new int[1050000];
int arr2[] = new int[1050000];
long startTime, endTime;
for (int i = 0; i < arr1.length; i++) {
arr1[i] = i + 1;
}
startTime = System.currentTimeMillis();
for (int i = 0; i < arr1.length; i++) {
arr2[i] = arr1[i];
}
endTime = System.currentTimeMillis();
System.out.println(“Time for manual copy: ” + (endTime-startTime) + ” ms.”);
startTime = System.currentTimeMillis();
System.arraycopy(arr1, 0, arr2, 0, arr1.length);
endTime = System.currentTimeMillis();
System.out.println(“Time for manual copy: ” + (endTime-startTime) + ” ms.”);
System.gc(); //force garbage collector
System.setIn(new FileInputStream(“temp.txt”));
System.exit(0);
}
}
Distributed by Meruvian Education
Output Percobaan 7 :
Distributed by Meruvian Education

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