Frequently Used Static Constants/Methods
Math.PI
Math.random()
Math.pow(a, b)
System.currentTimeMillis()
System.out.println(anyValue)
JOptionPane.showMessageDialog(null,
message)
JOptionPane.showInputDialog(
prompt-message)
Integer.parseInt(string)
Double.parseDouble(string)
Arrays.sort(type[] list)
Arrays.binarySearch(type[] list, type key)
Array/Length/Initializer
int[] list = new int[10];
list.length;
int[] list = {1, 2, 3, 4};
Multidimensional Array/Length/Initializer
int[][] list = new int[10][10];
list.length;
list[0].length;
int[][] list = {{1, 2}, {3, 4}};
Ragged Array
int[][] m = {{1, 2, 3, 4},
{1, 2, 3},
{1, 2},
{1}};
String Class
String s = "Welcome";
String s = new String(char[]);
int length = s.length();
char ch = s.charAt(index);
int d = s.compareTo(s1);
boolean b = s.equals(s1);
boolean b = s.startsWith(s1);
boolean b = s.endsWith(s1);
String s1 = s.trim();
String s1 = s.toUpperCase();
String s1 = s.toLowerCase();
int index = s.indexOf(ch);
int index = s.lastIndexOf(ch);
String s1 = s.substring(ch);
String s1 = s.substring(i,j);
char[] chs = s.toCharArray();
String s1 = s.replaceAll(regex,repl);
String[] tokens = s.split(regex);
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Object Class
Object o = new Object();
o.toString();
o.equals(o1);
File Class
File file =
new File(filename);
file.exists()
file.renameTo(File)
file.delete()
Text File Output
PrintWriter output =
new PrintWriter(filename);
output.print(...);
output.println(...);
output.printf(...);
Text File Input
Scanner input = new Scanner(
new File(filename));
ArrayList Class
ArrayList<E> list = new ArrayList<E>();
list.add(object);
list.add(index, object);
list.clear();
Object o = list.get(index);
boolean b = list.isEmpty();
boolean b = list.contains(object);
int i = list.size();
list.remove(index);
list.set(index, object);
int i = list.indexOf(object);
int i = list.lastIndexOf(object);
printf Method
System.out.printf("%b %c %d %f %e %s",
true, 'A', 45, 45.5, 45.5, "Welcome");
System.out.printf("%-5d %10.2f %10.2e %8s",
45, 45.5, 45.5, "Welcome");
Comparable Interface
c.compareTo(Comparable)
c is a Comparable object
Java Quick Reference
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