JarCastingjava-utils
Python-inspired utility functions and classes for Java.
Enumerate
(inspired by Python's enumerate function)
The static methods of the com.github.fracpete.javautils.Enumerate class allows to associate elements of an array, a java.lang.Iterable or java.util.Iterator with an index, by outputting a container class with the two of them. You can use different starting indices and step sizes between elements:
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import com.github.fracpete.javautils.enumerate.Enumerated;
import static com.github.fracpete.javautils.Enumerate.enumerate;
...
String[] array = new String[]{"a", "b", "c"};
List<String> list = new ArrayList<>(Arrays.asList(array));
// Array
System.out.println("\nWrapping Array:");
for (Enumerated<String> e: enumerate(array))
System.out.println(e.index + ": " + e.value);
// Iterable
System.out.println("\nWrapping Iterable:");
for (Enumerated<String> e: enumerate(list))
System.out.println(e.index + ": " + e.value);
// Iterable (start=1)
System.out.println("\nWrapping Iterable (start = 1):");
for (Enumerated<String> e: enumerate(list, 1))
System.out.println(e.index + ": " + e.value);
// Iterable (start=0, step = -1)
System.out.println("\nWrapping Iterable (start = 0, step = -2):");
for (Enumerated<String> e: enumerate(list, 0, -2))
System.out.println(e.index + ": " + e.value);
// Iterator
System.out.println("\nWrapping Iterator:");
Iterator<String> iter = list.iterator();
for (Iterator<Enumerated<String>> it = enumerate(iter); it.hasNext(); ) {
Enumerated<String> e = it.next();
System.out.println(e.index + ": " + e.value);
}
Generated output:
Wrapping Iterable:
0: a
1: b
2: c
Wrapping Iterable (start = 1):
1: a
2: b
3: c
Wrapping Iterable (start = 0, step = -2):
0: a
-2: b
-4: c
Wrapping Iterator:
0: a
1: b
2: c
Struct
(inspired by Python's tuples)
The static struct methods of the com.github.fracpete.javautils.Struct class allow you to quickly wrap two to five values in a container class. You can also wrap the key/value pairs of a map with that, to quickly iterate over a map.
import java.util.HashMap;
import java.util.Map;
import com.github.fracpete.javautils.struct.MapStruct;
import com.github.fracpete.javautils.struct.Struct2;
import static com.github.fracpete.javautils.Struct.pairs;
import static com.github.fracpete.javautils.Struct.struct;
...
public static Struct2<Integer,Integer> return2int(Integer value) {
return struct(value, value * value);
}
public static void main(String[] args) throws Exception {
System.out.println("\nSimple struct");
int value = 12;
System.out.println("value=" + value);
Struct2<Integer,Integer> i2 = return2int(value);
System.out.println("container: " + i2);
System.out.println("value1: " + i2.value1);
System.out.println("value2: " + i2.value2);
System.out.println("\nMap key/value pairs");
Map<String,String> map = new HashMap<>();
map.put("C", "Hello");
map.put("B", "World");
map.put("A", "Sup!");
for (MapStruct<String,String> s: pairs(map))
System.out.println("k=" + s.key + ", v=" + s.value);
}
Generated output:
Simple struct
value=12
container: value1=12, value2=144
value1: 12
value2: 144
Map key/value pairs
k=A, v=Sup!
k=B, v=World
k=C, v=Hello
Reflection
The com.github.fracpete.javautils.Reflection class offers static methods to simplify reflection a bit:
-
instantiating objects:
newInstanceimport static com.github.fracpete.javautils.Reflection.newInstance; Object file1 = newInstance("java.io.File", new Class[]{String.class}, new Object[]{System.getProperty("java.io.tmpdir")}); System.out.println("newInstance: " + file1); Object file2 = newInstance("java.io.File", new Class[]{String.class}, new Object[]{System.getProperty("java.io.tmpdir") + "/some.txt"}); System.out.println("newInstance: " + file2);
-
method calls (with return value):
functionimport static com.github.fracpete.javautils.Reflection.function; Object name = function(file1, "getName"); System.out.println("name: " + name); int comparison = function(file1, "compareTo", new Class[]{File.class}, new Object[]{file2}); System.out.println("f1.compareTo(f2): " + comparison);
-
method calls (without return value):
procedureimport static com.github.fracpete.javautils.Reflection.procedure; procedure(file2, "deleteOnExit"); System.out.println("called deleteOnExit");
Maven
Add the following dependency to your pom.xml:
<dependency>
<groupId>com.github.fracpete</groupId>
<artifactId>java-utils</artifactId>
<version>0.0.3</version>
</dependency>