View source for Java13/Examples

This is an informal page listing examples of features that are implemented by the Java 13 Support. You are welcome to try out these examples. If you find bugs, please file a bug after checking for a duplicate entry [http://eclip.se/fP here]

<b>NOTE:</b>
* Switch expression, Enhanced switch statement and Multi-constant case labels are <b>Preview features</b> in Java 13. They are not enabled by default and can by enabled using <b>--enable-preview</b>.
* TextBlock is also another preview feature in Java 13.
* In Eclipse, <b>--enable-preview</b> can be enabled from the Preferences. It is implicitly added while launching a java program if the feature has been enabled for the project/workspace.

{| class="wikitable"

! scope="row" style="width: 15%;" |
| style="width: 60%; text-align: center" | '''Feature''' / Steps
! style="width: 25%;" | Expected Result
|-
! colspan="3" | The Pre-requisite: Java 13 JRE Support
|-
! scope="row" | Add Java 13 JRE
| Use Window -> Preferences-> Java -> Installed JREs -> Add... <br>
<br>
[[File:FileAddJ13.png]]
<br>
[note: Eclipse -> Preferences in Mac / Window -> Preferences in Windows]
| Java 13 JRE recognized as a valid JRE
|-
! scope="row" | Project JRE
| In Package Explorer Use project's context menu and add Java 13 JRE  || JRE specific (eg Object) gets resolved in the project.
|-
! scope="row" | Package Explorer
| Go to Package Explorer and expand the Java 13 JRE || Modules (eg java.base etc) are listed in the package explorer view
|-
! colspan="3" | The First Step: Java 13 Compliance
|-
! scope="row" | Set Project Compliance in Package Explorer
| Context Menu of Project -> Properties -> Set project-specific, drop down to 13
<br>
<br>
[[File:j13.compliance.png]]
|13 is shown in the drop down list.
A checkbox to enable preview features is available on the preference page.
|-
! colspan="3" | Preview Feature: Switch Expressions, Enhanced Switch Statement and Multi-Label Case Statements.
|-
! scope="row" | Positive Compilation 1 (Switch Statement with multi-label case with colon)
| Use the following code:
<source lang="java">
public class X {
    public void foo(int i) {
    	switch (i) {
    		case 0, 1, 2: System.out.println("Hello");
    		default :  System.out.println("World");
    	}
    }
    public static void main(String[] argv) {
        new X().foo(2);
    }
}</source> 

<br>
<br>
[[File:switch-statement-multi.png]]
| Code compiles (with a preview warning) and while running prints both "Hello" "World"
|-
! scope="row" | Positive Compilation 2 (Switch Statement with case with arrow)
| Use the following code:
<source lang="java">
public class X {
    @SuppressWarnings("preview")
	public void foo(int i) {
    	switch (i) {
    		case  2 -> System.out.println("Hello");
    		default ->  System.out.println("World");
    	}
    }
    public static void main(String[] argv) {
        new X().foo(2);
    }
}</source> 

<br>
<br>
[[File:switch-statement-arrow.png]]
| Code compiles (with a preview warning) and while running prints only "Hello" (because a break is implicit after every case with an arrow.
|-
! scope="row" | Positive Compilation (Switch Expression)
| Use the following code:
<source lang="java">
public class Test {
	
	enum Day {
		MON, TUE, WED, THUR, FRI, SAT, SUN
	};
	
	@SuppressWarnings("preview")
	public String getDay_1 (Day today) {
		String day = switch(today) {
			case MON, TUE, WED, THUR, FRI -> "Weekday";
			case SAT, SUN -> "Weekend";
		};
		return day;
	}
}
</source> 

<br>
<br>
[[File:switch-exp.compile.png]]
| Code compiles
|-
! scope="row" | Compiler error Case
| 
<source lang="java">
public class Test {
	
	enum Day {
		MON, TUE, WED, THUR, FRI, SAT, SUN
	};
	
	public String getDay_1 (Day today) {
		String day = switch(today) {
			case MON, TUE, WED, THUR, FRI-> "Weekday";
			case SAT, SUN->"Weekend";
		};
		return day;
	}
}
</source>
<br>
<br>
[[File:enable-preview.error.png]]
| Compiler error is shown for preview feature.
Quick fix is available to enable the preview feature in the preferences.
|-
! scope="row" | Compiler Warning Case
| 
<source lang="java">
public class Test {
 
	enum Day {
		MON, TUE, WED, THUR, FRI, SAT, SUN
	};
 
	public String getDay_1 (Day today) {
		String day = switch(today) {
			case MON, TUE, WED, THUR, FRI : yield "Weekday";
			case SAT, SUN : yield "Weekend";
		};
		return day;
	}
}
</source>
<br>
<br>
[[File:switch.preview.warning.compile.yield.png]]
| Compiler warning is shown for preview feature
|-
! scope="row" | Compiler Error Case
| 
<source lang="java">
public class Test {
	
	enum Day {
		MON, TUE, WED, THUR, FRI, SAT, SUN
	};
	
	@SuppressWarnings("preview")
	public String getDay_1 (Day today) {
		String day = switch(today) {
			case MON : yield "Weekday";
			case SAT, SUN : yield "Weekend";
		};
		return day;
	}
}
</source>
[[File:switch.cover-all-cases.error.yield.png]]
| Compiler error is shown
|-
! colspan="3" | Preview Feature: Text Blocks
|-
! scope="row" | Text Block Example
| Compile and run the following code:
<source lang="java">
@SuppressWarnings("preview")
public class Test {
	public static void main(String[] args) {
		String tb = """
		Hello
		World
				""";
		System.out.println(tb);
	}
}
</source> 

<br>
<br>
[[File:textblock.png]]
| Code compiles prints both "Hello" "World" as it is - notice that "World" is printed in the next line.
|-
! scope="row" | Text Block Compilation Error Example
| Use the following code:
<source lang="java">
public class Test {
	public static void main(String[] args) {
		String tb = """
		Hello
		World
				"";
	}
}</source> 

<br>
<br>
[[File:textblock.error.png]]
|Compilation error - text block not closed properly
|-