04 Sequenzen

Strings are immutable, that means we always receive a copy as the output of the function.

String original = "Hello World";
String sub = original.substring(0, 5);  // Creates NEW string "Hello"
 
System.out.println(original);  // "Hello World" (unchanged)
System.out.println(sub);       // "Hello"

String methods that return String

• substring(i1, i2) or substring(i1) which returns the substring from i1 to i2 (or end of String is omitted).
• toLowerCase
• toUpperCase
• stripLeading und stripTailing remove spaces at the beginning (resp. end) of the String.

String methods that return int

• length() returns the number of characters in the string
• `indexOf()

String methods that return boolean

String comparisons

Do not compare strings (or any non-primitive types) with == in Java as this compares their references and not the actual string value. Use .equals() for this.

Arrays

We can initialise arrays directly with the following syntax: int[] test = {1, 2, 3, ..., 4};.

Methods

You can use helper methods from java.util.Arrays:

• To compare arrays, also use Arrays.equals(1, 2).
• Create a copy Arrays.copyOf(arr, l)
• Sort using Arrays.sort(arr)
• To String using Arrays.toString(arr) or Arrays.deepToString(arr).