java String類說明

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java String類說明

 

 

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String 類

 

String

public final class String
    implements java.io.Serializable, Comparable<String>, CharSequence,
               Constable, ConstantDesc {  //String類用final修飾，不可被繼承修改

    @Stable
    private final byte[] value;           //使用位元組陣列儲存字串內容
                                          //value用final修飾，指向內容不可修改

    /**
     * The identifier of the encoding used to encode the bytes in
     * {@code value}. The supported values in this implementation are
     *
     * LATIN1
     * UTF16
     */
    private final byte coder;             //字串編碼方式，可選值：LATIN1、UTF16


    /** Cache the hash code for the string */
    private int hash;                     //快取字串hash值，預設0

    /**
     * Cache if the hash has been calculated as actually being zero, enabling
     * us to avoid recalculating this.
     */
    private boolean hashIsZero;           //hash是否為0，預設false
                                          //首次返回hashcode後，會用hash快取，隨後獲取hashcode時，直接返回hash，避免重複計算

    @java.io.Serial
    private static final long serialVersionUID = -6849794470754667710L;


    static final boolean COMPACT_STRINGS; //是否壓縮字串，預設：true

    static {
        COMPACT_STRINGS = true;
    }


    @java.io.Serial
    private static final ObjectStreamField[] serialPersistentFields =
        new ObjectStreamField[0];

 

 

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