diff options
Diffstat (limited to 'java.html.markdown')
| -rw-r--r-- | java.html.markdown | 31 |
1 files changed, 28 insertions, 3 deletions
diff --git a/java.html.markdown b/java.html.markdown index 6487d862..12de0c73 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -95,6 +95,12 @@ public class LearnJava { // Byte - 8-bit signed two's complement integer // (-128 <= byte <= 127) byte fooByte = 100; + + // If you would like to interpret a byte as an unsigned integer + // then this simple operation can help + int unsignedIntLessThan256 = 0xff & fooByte; + // this contrasts a cast which can be negative. + int signedInt = (int) fooByte; // Short - 16-bit signed two's complement integer // (-32,768 <= short <= 32,767) @@ -102,7 +108,7 @@ public class LearnJava { // Integer - 32-bit signed two's complement integer // (-2,147,483,648 <= int <= 2,147,483,647) - int fooInt = 1; + int bazInt = 1; // Long - 64-bit signed two's complement integer // (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807) @@ -110,7 +116,9 @@ public class LearnJava { // L is used to denote that this variable value is of type Long; // anything without is treated as integer by default. - // Note: Java has no unsigned types. + // Note: byte, short, int and long are signed. They can have positive and negative values. + // There are no unsigned variants. + // char, however, is 16-bit unsigned. // Float - Single-precision 32-bit IEEE 754 Floating Point // 2^-149 <= float <= (2-2^-23) * 2^127 @@ -190,7 +198,20 @@ public class LearnJava { builderConcatenated.append("the StringBuilder class."); System.out.println(builderConcatenated.toString()); // only now is the string built // Output: You can use the StringBuilder class. - + + // StringBuilder is efficient when the fully constructed String is not required until the end of some processing. + StringBuilder stringBuilder = new StringBuilder(); + String inefficientString = ""; + for(int i = 0 ; i < 10; i++){ + stringBuilder.append(i).append(" "); + inefficientString += i + " "; + } + System.out.println(inefficientString); + System.out.println(stringBuilder.toString()); + // inefficientString requires a lot more work to produce, as it generates a String on every loop iteration. + // Simple concatenation with + is compiled to a StringBuilder and toString() + // Avoid string concatenation in loops. + // #3 - with String formatter // Another alternative way to create strings. Fast and readable. String.format("%s may prefer %s.", "Or you", "String.format()"); @@ -827,6 +848,10 @@ The links provided here below are just to get an understanding of the topic, fee * [Java Code Conventions](https://www.oracle.com/technetwork/java/codeconvtoc-136057.html) +* New features in Java 8: + * [Lambda expressions (functional programming)](https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html) + * [Date and time API (java.time package)](http://www.oracle.com/technetwork/articles/java/jf14-date-time-2125367.html) + **Online Practice and Tutorials** * [Learneroo.com - Learn Java](http://www.learneroo.com) |