diff --git a/Kasutus.class b/Kasutus.class
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diff --git a/Kasutus.java b/Kasutus.java
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+++ b/Kasutus.java
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+public class Kasutus{
+    public static void main(String[] args) {
+        Liides ruutjuureArvutaja = new Ruutjuur();
+        System.out.println("Ruutjuur arvust on: "+ ruutjuureArvutaja.f(100));
+    }
+}
+
+/* 
+[gittkaus@greeny t07liides]$ javac *.java
+[gittkaus@greeny t07liides]$ java Kasutus
+Ruutjuur arvust on: 10.0
+*/
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diff --git a/Liides.class b/Liides.class
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diff --git a/Liides.java b/Liides.java
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+++ b/Liides.java
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+public interface Liides{
+	public double f(double x);
+}
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diff --git a/Ruutjuur.class b/Ruutjuur.class
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diff --git a/Ruutjuur.java b/Ruutjuur.java
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+public class Ruutjuur implements Liides{
+    public double f(double x){
+        return Math.sqrt(x);
+    }
+}
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