test/jdk/java/lang/StringBuilder/CharAt.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 2 along with this work; if not, write to the Free Software Foundation,
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/*
 * @test
 * @bug 8271732
 * @summary Basic test that charAt throws IIOBE as expected for out of bounds indexes.
 * @run testng CharAt
 */

import java.util.List;

import org.testng.annotations.Test;
import org.testng.annotations.DataProvider;
import static org.testng.Assert.*;

public class CharAt {

    /**
     * StringBuilder/-Buffer.charAt throws:
     * IndexOutOfBoundsException - if index is negative or greater than or equal to length().
     * the test inputs, expected to throw IndexOutOfBoundsException.
     */
    @Test
    public void charAtIIOBE() {
        StringBuilder sb = new StringBuilder("test");
        StringBuffer sbuf = new StringBuffer("test");

        StringBuilder sbUtf16 = new StringBuilder("\uFF34est"); // Fullwidth Latin Capital Letter T
        StringBuffer sbufUtf16 = new StringBuffer("\uFF34est");

        List<Integer> outOfBoundsIndices = List.of(Integer.MIN_VALUE, -2, -1, 4, 5, Integer.MAX_VALUE);

        for (int index : outOfBoundsIndices) {
            try {
                sb.charAt(index);
                fail("StringBuilder.charAt index: " + index + " does not throw IOOBE as expected");
            } catch (IndexOutOfBoundsException ex) {
                // OK
            }

            try {
                sbUtf16.charAt(index);
                fail("StringBuilder.charAt index: " + index + " does not throw IOOBE as expected (UTF-16)");
            } catch (IndexOutOfBoundsException ex) {
                // OK
            }

            try {
                sbuf.charAt(index);
                fail("StringBuffer.charAt index: " + index + " does not throw IOOBE as expected");
            } catch (IndexOutOfBoundsException ex) {
                // OK
            }

            try {
                sbufUtf16.charAt(index);
                fail("StringBuffer.charAt index: " + index + " does not throw IOOBE as expected (UTF-16)");
            } catch (IndexOutOfBoundsException ex) {
                // OK
            }
        }
    }
}